Too many parallel nested transactions

Just recentally we have started to get dump files with the
following description:

Description: Too many parallel nested transactions

When this happens and the dump files start to get created the server
starts begins to time out making the applications crash.

Does anyone have
any suggestions on how/what i can do to try and track down this error so i can
see what caused it and keep it from happening in the future.

SQL Server: 2005 Standard 64x

Thanks,
John