So, I had the same error tryng to add OCUM 7.1 integrated with PM 7.1 as a data source. Another symptom I had was that I could no longer pair clusters from OCUM to PM (both VMware ovas). This began after upgrading from 6.4 (I think).
The fix for both pairing and connecting to WFA 4.1RC1 was to download the full install of OCUM 7.1 and PM 7.1, installing fresh, and now all seemingly works. It's tedious as I have to repopulate, re-tune alerting, and re-build UM reports.
If anyone tries this and has issue with adding the clusters to PM, you may need to delete the old application-record for Performance Manager by going into diag, typing application-record show.