I can't reproduce this on local installations but, just on demo.bestpractical.com, certain search queries error out on the rbind step due to a mismatch in column names. This may be an artifact of how that RT installation is set up but we should take a look at what's going on.
I think I can reproduce this with just a search like rt_ticket_search("Queue = 'General'") on demo.bestpractical.com.