One of the major changes between AppleTalk for VMS 2.0 and 2.0.5 is that the definition of an invalid packet was changed to exclude a large number of packets that had previously been accepted as valid. This was done because a number of the packets that were previously being accepted were actually very badly-formed packets and were causing the bridge process to crash.
However, things were tightened up so much that packets that valid were rejected. Version 2.0.6 resolves this, and you should get it from the same source from which you got version 2.0.5.
Using version 2.0.6 may resolve your problems. It is also possible that there are bad RTMP packets being generated on the network. In this case, you will continue to receive the warning messages. The ATKBRIDGE.LOG file will contain the actual packets that are being rejected, and you can often identify the sender from the data in this log file.
Either way, you should be using the latest version (2.0.6) on both VAX systems. Version 2.0 has a large number of problems, so the machine running that version should be upgraded.
Finally, if at all possible, you should move everything to AppleTalk Phase 2 and PATHWORKS (formerly LanWORKS). That is the direction we are headed, and you should use AppleTalk for VMS 2.0.6 and 2.1 only as interim releases, until you are ready to install PATHWORKS.