Active Power closed down 12.12% on Friday - the worst performing AEI stock of the day. It appears that a central cause is that preliminary findings showed it backdated certain stock option grants, and that it expects to incur additional stock-based compensation charges.

And the article continues;

"... it has not been determined whether any such charges would require a restatement of prior financial statements".

This is a great shame for a company which produces the largest commercially available flywheels - which has enjoyed some success, as I blogged about here last August. And the fact that flywheels still have enormous potential in the hybrid vehicle market.