* Q1 loss/shr $0.13 vs $0.02 profit last year

* Cuts 2009 outlook

* May have to restate for revolver classification

* Same-store sales down 7 pct

* Shares tumble 20 percent

May 18 (Reuters) - Clothing retailer American Apparel Inc (APP.A: Quote, Profile, Research) swung to a first-quarter loss, cut its full-year outlook and said it may have to restate prior financial statements due to the classification of its revolving credit facility, triggering a 20-percent slide in its stock.

The company, which earlier in the day settled a suit bought by film director Woody Allen for $5 million, said operating expenses rose 21 percent to $69.3 million in the quarter, while sales were up 2.4 percent to $114.3 million.

For the quarter ended March 31, American Apparel, which operates over 265 retail stores in 19 countries, posted a net loss $9.0 million, or 13 cents a share, compared with a profit of $1.1 million, or 2 cents a share, a year ago.

American Apparel said any change to the classification of its revolving credit as a long-term obligation and certain other balance sheet matters, may result in a restatement of prior financial statements, but is not expected to hurt net cash flows, cash position, revenues or net income.