If you've not edited (using manual or XGUI) <your gmod server path>/data/ulx/config.txt/(ulx votemapMapmode) from mode 1, it's default, then ANY map IN <your gmod server path>/data/ulx/votemaps.txt will NOT be listed as a map to vote on.
That means, if you've REMOVED CS:S maps...they WILL SHOW.
From the sample config.txt file in the addons/ulx/data/ulx/ folder, which says to copy/edit in <your gmod server path>/data/ulx/
ulx votemapMapmode 1 = Use all maps but what's specified in votemaps.txt, 2 = Use only the maps specified in votemaps.txt.
If you've already edited votemaps.txt to only maps you want voted on, change that config.txt to 2.
(Also, Meg, Stick, I just noticed our votemaps.txt file still mentions the old server.cfg.. may want to update to mantion new config.txt, I would, but haven't installed SVN since last OS img)