Subject Errors in firebird.log

Hi, I have firebird 2.5.4 super server on Win 2007 SP2 32bit server.

I have to reinstall it - because it occasionally (app. 4x a week) falls and needs to restart whole server.

Now it looks much better, but after 5 days of service there are these rows in firebird.conf

SERVER01 (Server)    Sun May 17 16:43:51 2015
    Fatal exception during clumplet dump: Invalid clumplet buffer structure: spb in service attach should begin with isc_spb_version1 or isc_spb_version

SERVER01 (Server)    Sun May 17 16:43:51 2015
    Plain dump starting with offset 924: zlmPQLfQpWkDQTECIrQgtkslFVlPFBbBDGXAqlZZhnZyhDFAVegCOGKyAJvqmiBcXBDtOUJiRLVAuPIzKizgbkDQsvuGpJoFlBnk

This error is 5 times a day on Sunday.

What happened ?? What should I do to prevent this error?

Thank you in advance.

Best regards, Tom