strange nhibernate exception?

Question

Hi
i am gettin a strange exception in may windows service application, but it was working fine for a long time and suddenly gave this error:

"(0xc0000005 at address 5A17BF2A): likely culprit is 'PARSE'."

2010-05-11 07:00:03,154 ERROR [0   ] [NHibernate.Cfg.Configuration.LogAndThrow] - Could not compile the mapping document: xxxx.hbm.xml
NHibernate.MappingException: Could not compile the mapping document: xxxx.hbm.xml ---> System.InvalidOperationException: Unable to generate a temporary class (result=1).
error CS0001: Internal compiler error (0x80004005)
error CS0001: Internal compiler error (0xc0000017)
error CS0583: Internal Compiler Error (0xc0000005 at address 5A17BF2A): likely culprit is 'PARSE'.
error CS0586: Internal Compiler Error: stage 'PARSE'
error CS0587: Internal Compiler Error: stage 'PARSE'
error CS0587: Internal Compiler Error: stage 'BEGIN'

any could help me in understanding this issue/error why it came and to solve it?

Thanks
nRk