Performance Point Server 2007 stopped allowing the importing of KPI's from SSAS Cube

Question

I use Performance Point server at work.  When building scorecards, I regularly import KPI's from SSAS cubes.  I am suddenly unable to Import KPI's everything else works as expected, but when I try to import KPI's I get the following error message:

"An unknown error has occurred.  If the problem persists contact an administrator.  There may be additional information in the server event log."

This issue can be fixed by reverting to an earlier copy of the database, but this is not a practical solution.  We tried a couple of times and the problem comes back within a day.

Any help tracking this problem down would be appreciated.