Oh dear, this one's a bit of a deal-breaker isn't it?
The problem goes all the way down to the CodeIgniter query builder class and the way in which GC is using it.
GC is calling ci->where() when you have a where() defined.
Do a search from that list, and GC makes repeated calls to ci->or_like() which CodeIgniter just chains together.
Result? Search in GC is completely broken if you use ->where()
This looks like a structural problem in GC and I can't see it being fixed any time soon :-(