I haven't noticed any problems with our Unity UM 5.0(1) but see in the logs every 3 or 4 minutes this error. We have 144 ports/1200 subscribers and about 10-20 calls up at given time.
Event Type: Error
Event Source: CiscoUnity_ConvSub
Event Category: Network
Event ID: 1000
Time: 3:59:53 PM
An unexpected error has occured while a subscriber is on the phone with Unity. This can potentially result in the subscriber hearing the failsafe conversation. Technical details are - CAvSValidateID::ValidateSubType returned [0x80004005] on line 658 of file H:\views\CUESB1_view\un_Conv1\Scripted\ConvSub\SubSignIn.cpp.