After a relatively smooth holiday debut, Europe's new currency was put to the test Wednesday amid checkout delays, ATM breakdowns and armed robberies for euro's first big shopping day.

The euro got its roughest start in Austria, where the country's 2,400 cash machines broke down because of overuse by customers trying to get new euro notes.

The Austrian press agency APA said the machines stopped working at 1315 GMT (9:15 am EDT) when a central computer crashed. The breakdown was caused by the unusually high number of transactions, and the problem was fixed shortly afterwards.

Crime Spree

A number of  major robberies also hit Europe's new currency as it went into circulation across most of the European Union.

In Greece, a gunman stole $68,400 worth of euros from a post office savings branch, and thieves hit a rural bank and an ATM machine in Ireland.

Brandishing a pistol, a man forced a cashier at the savings branch in the northern Athens suburb of Holargos to fill two bags with euro notes before fleeing on foot, police said. He also stole a small amount of drachmas, which are still legal tender until the end of February. No one was injured.

In Ireland, three assailants, two of them armed with a hammer and a knife, threatened staff at a branch of Allied Irish Banks before grabbing about 2,000 euros, worth $1,800, from a till and escaping in a waiting car.

Already on Monday, a German bank robber seized tens of thousands of euros hours before the midnight launch of the single currency. The cash, stored in a savings bank in the northern German town of Pinneberg, was sealed in plastic and had just been delivered by the regional central bank for public distribution.

Elsewhere in Europe, confusion, angry scenes at cash registers and resignation were on the menu, although things remained relatively orderly and legal.

Lines formed at the Spar supermarket in the Amsterdam suburb of Buitenveldert, as shoppers struggled to sort the new coins in their purses and cashiers double-checked change.

"We ask for your understanding if paying at the checkout takes a bit longer than usual. Our cashiers have to get used to the euro too," read a sign at the checkout.

At the nearby Burcht drugstore, the manageress said people were keen to pay with euros despite being able to use guilders. "People think it's fun to pay in euros, they're treating it like Monopoly money, like a game," she said.

In central Rome, customers were paying in lire only at a pharmacy on Via Gambero, forcing the staff to convert back from euro prices.

"It's a bit chaotic," said pharmacist Roberta Panocchi, as she punched in the euro price for a tube of toothpaste into the register, then figured out the lira price for her customer, Valentina Monaco.

A shortage of cash remains the biggest nightmare for the retail giants of the euro zone.

Effectively, it is the retailers, not the banks, which bear the brunt of injecting euro coins into the economy and withdrawing the 12 legacy currencies.

Most of the banknotes will come from cash dispensers and over the counter at banks, but the coins are a far more serious problem. There are many more of them -- over 51 billion coins, including reserves, versus 15 billion plus notes.

Heavy Coins

The sheer weight of the coins has caused its own problems. France's top department store chain Galeries Lafayette had to reinforce the floors at some provincial outlets and buy new safes to accommodate the euro.

Metro, the largest German retailer, had to freight 700 tons of coins, while rival ReWe ordered a kiloton. Shopkeepers reported the majority of customers were still unloading their old, national currencies.

"Most people are paying in German marks, but ... it's only the first day," said Mehmed Tasar, serving croissants and sandwiches to morning commuters in Frankfurt. "In another week there won't be any German marks here any more."

The euro, a decade in the works, became legal tender with the dawning of the new year. It is perhaps the most concrete evidence of Europe's transition from a divided continent to a team of nations working toward the same goals.

The 12 European Union nations that adopted the euro are parting with currencies that have long histories -- such as Greece's drachma, which stretches back 2,600 years.

National currencies will circulate side by side with the euro for up to two months to help ease the transition, but European Central Bank officials are hoping that most people will use only euros after the first two weeks.

The foot soldiers in the switch will be Europe's retailers, who are expected to take in the old and hand out the new in change to help remove national currencies from circulation.

But that wasn't happening everywhere.

"My problem is I don't have enough bills," said Mourad Mahoudi, who runs a grocery near the European Union headquarters in Brussels.

When people come in with 50 euro notes (worth about $44.50), he is forced to hand out change in Belgian francs, going against the whole spirit of the operation. "But I hope to get to the bank later in the day," he said.

At one Madrid cinema, the cashier insisted on paying back change in pesetas, explaining she was trying to get rid of the old coins too.

French Bank Tellers on Strike

Complicating matters in France, five main banking unions began a one-day strike Wednesday to demand higher pay, more hiring and better security.

But French Finance Minister Laurent Fabius said participation in the strike was "very limited," with almost all workers on the job at three of France's major banks. Bank of France governor Jean-Claude Trichet said that overall, the country's switch to the new currency has "gone over very well."

"We need a euro that inspires confidence and I think we have achieved that," Trichet said.

Two of the six Bank of Italy unions also walked out in an attempt to force mediation of a contract dispute. However, bank officials said branches in major cities would remain open.

The European Union's executive Commission called the first day of the currency switch a success, saying no major glitches were reported from any of the 12 euro-using nations. But the real test was Wednesday, the first day of business following the holiday.

Reuters and the Associated Press contributed to this report.