Hey,
I think I found a bug. If you have a struct completition list open (e.g. after typing the dot after foo where foo is an instance of a struct) you normally get a completion list with only the members. If you then type further until you typed the number of characters needed for the normal list, then the normal list pops up (the one which has all sorts of stuffs like functions etc) and the struct-specific one is destroyed.
I think this is a bug because the current code tries to proted the struct-list.
I have a proposed fix in my git repo, you can see it here: http://repo.or.cz/w/geany-mirror/kugel-geany.git/commit/e6a4fd1ad407d9c07bf9...
The problem seems to be that it only checks for an open list for the tag completion, not for the "documents' words" one. Also, the check before the tag completion list seems wrong too so I fixed it.
With that patch, everything works alright again for me.
Best regards.