ULX uses more than just /addons/ folders, so if during 're-install' you didn't delete/back up your <gmod server>/data/ulx files...they remain.
That being said, if they aren't working in menu, not sure re-installing would fix them.
Until Stickly Man (or Megiddo, if he feels so inspired) can look at the XGUI code for adverts to see why they aren't updating in menu, you can manually edit them in your gmod/data/ulx/adverts.txt file.
While at it, when running server and attempting to load the menu, editing adverts, check for any server console errors. (or client).