Error 500 when not clear XML cache on AdminPayment

[Janekx]

Hi, 

I have issue with 1.6.1.23

Every time i need access AdminPayment i got error 500 and no other messages, i tried dev true mode , php loging. No sigh of error. 

I doesn happend when clear XML mainly one of files  untrusted_modules_list.xml or trusted_modules_list.xml

If delete this files or one of them the AdminPayment loads well. 

Any idea? 

Thanks