After applying Patch 5 for ITSM, our Plugin Server stopped working and anything that required a (.dll) Plugin started to produce ARERR [8755]. As a result we can no longer access our AR Admin Console for any server confifuration.

BMC /Remedy has escalated this to their 3rd level engineering with little to no luck fixing this.

Is anyone else experiencing a similar problem?

Have not seen that. Did you try Patch006, perchance? or 7.0.3?