merge feature of FTM

after searching for hints for an individual, I find something I might want to merge into my tree and the right panel just spins on many of the entries. When it works, I can compare names, dates, spouse and parents, etc.

some work and some don't on FTM 2011. Is it the other people's trees or something wrong with my software or tree?

will upgrading fix this?

thanks for any advice!
Margaret