I am also having difficulty with the Search function.  It searched correctly the first time I tried a search.  The second time it gave me nothing in particular.  I think it didn't even run a search.  After closing and re-opening the program, the third time it did a search but returned a bunch of pictures that had no relation to what I was looking for.  I am running XP Pro, SP2, 20-day trial of Photo Mechanic.  Beautiful looking software and lots I like, but the proof is in the testing.  So far, um...
Are there different brands of IPTC?  Because some of the fields I have filled from other software, such as copyright and Source URL, do not show up in Photo Mechanic.