SCOM: Peculiar Error Upgrading from SP1 to R2 –Cross Platform management pack(s) are imported…

This is probably pretty rare, but I came upon a peculiar error today while upgrading an Operations Manager 2007 SP1 RMS to R2. The error message was:

Product: System Center Operations Manager 2007 R2 — System Center Operations Manager Cross Platform management pack(s) are imported in this management group. Please delete these management packs(s) before upgrading to System Center Operations Manager R2.

This wouldn’t be a surprise except for the fact that there were no Cross Platform MP’s imported, and furthermore, since the current server was 2007 SP1, Cross Platform MP’s couldn’t even be imported in the first place. It took me a bit to figure out, but it turns out the problem was the fact that there was a custom management pack (for SNMP monitoring) with the string UNIX in the MP name. It looks like the installation package is checking installed MP’s for pretty generic strings to determine if Cross Platform MP’s are imported (presumably applying only to pre-RTM versions of R2). I had to remove the custom MP with the term UNIX in the name and rerun the upgrade.

Note:  Anders Bengtsson has described a situation with the same error when upgrading the second node in an RMS cluster, here.