> Thu Apr 15 13:36:26 2010
> Fatal lock manager error: invalid lock id (2413696), errno: 0

Please, confirm :
a) did you query monitoring tables (mon$xxx) at this database ? if yes, how often ?
b) is file fb_lock_table.dump you put at ftp corresponds to the error above ? i.e. its creation time is the same as time of error ?

Regards,
Vlad

PS i've started 10 instances of your app (using fresh FB 2.5 Win64 build), lets wait for results