well I'm experiencing the same issue, in my case it looks like the gallery is only showing (very) recent tags, like the tags I made within a week, the other ones don't show up...
when I didn't uploaded pictures with the tag for the gallery i get the same message...

I hope this problem doesn't take too long :o :o

EDIT: I noticed rtha the search is only doing weird when setted too "recent" , when you search for "relevance" there is no problem. maybe It's a good idea to make an option in simpleviewer too sort the tags by relevance or by recent , (if the API is allowing that ;) )