Adecco stunned investors with news of accounting irregularities at its Long Island-based North American headquarters. Adecco stock is tumbling in value and customers are growing nervous. Some feel the mistake could lead to a relocation of the company's headquarters.

Adecco is not revealing any details, which is causing some negative speculation. Since Adecco announced "material weaknesses" in financial controls on Jan. 12, its shares have lost more than a third of their value. At least eight class-action suits have been filed by shareholders, alleging the company inflated its stock by misrepresenting its finances.

One person close to the company revealed that the accounting methods used by Olsten and Adecco differed, causing some items to be entered incorrectly in the combined company's books, and there was no wrongdoing.

Officials of the company continue to decline comment.