Thanks Andrew, there seem to be a couple of things conspiring here:
a) You are right, I have thrown everything out of the library and added then folders successively back in, and indeed there were a few dodgy third party dxf's which seem to load forever and cause a hang problem. Displaying more than 100 icons per page does not seem to be a smart idea either.
b) I had also some seemingly valid files which did not load at all (maybe and older dxf format?) that the library does not support?
So, I am sort of happy on the tags page, however, I still do not see anything in the lower pane of the 'File system' tab - should there not be the icons for the selected folder? I really would like to organise my library with a folder structure - otherwise that tab is pretty useless as you then seemingly can only select through the tags and I see no way of mass-tagging the files.
Secondly, on the tags tab it appears that if you click repeatedly on the page arrows (bottom left) before the icons on the page have completely displayed the program goes on to generate icons back to the last fully displayed page. So if you quickly go to page 40 without ever waiting in between for instance, you may get 4000 icons (which of course takes forever). Feels like another look at the eventhandler is warranted.