First time I've seen this with dovecot-2.0.5. At 10:05 my auth server was having problems and I saw this:

Thu Oct 14 10:05:32 server dovecot[3536]: lda: Error: userdb lookup(userX): Request timed out Thu Oct 14 10:05:32 server dovecot[3536]: lda: Fatal: Internal error occurred. Refer to server log for more information.

OK, no problem there. But a few minutes later this crash that may or may not be related:

Thu Oct 14 10:09:39 server dovecot[150]: auth: Panic: file auth-request.c: line 78 (auth_request_set_state): assertion failed: (auth_request_state_count[request->state] > 0)

Here is a backtrace, unfortunately somewhat obfuscated by compiler optimization.

0 __pthread_kill + 10 1 pthread_kill + 95 2 abort + 143 3 i_set_failure_file + 274 4 i_set_failure_internal + 103 5 i_debug + 0 6 auth_request_initial + 0 7 auth_request_initial + 71 8 auth_penalty_anvil_callback + 207 9 anvil_client_connect + 364 10 io_loop_handler_run + 234 11 io_loop_run + 56 12 master_service_run + 27 13 main + 674 14 start + 52