Pretty close , but here's the real dirt-
Almost two years ago, the National Panhellenic Conference (all 26 member sororities) passed the "Alcohol-Free Housing" Resolution, in support of the many men's groups who were going dry in their houses in the fall of 2000. Basically in a nutshell, sororities can not attend an event at a fraternity house where alcohol was to be present. This includes parties, mixers, philanthropies etc. Only dry events were permissible, and if they wanted to have alcohol, a third-party vendor (ie. a bar) had to be contracted to host the closed event.
Some of the men's groups have not gone dry (yet), but have found that it has been harder to attract sororities to have a mixer with them as the women's groups are afraid of getting into trouble with their Headquarters. All the NPC groups have adjusted their Alcohol policies to not allow alcohol/frat houses, thus the big fear. As well, when individual members go to 'frat' parties', if more than just a few go, this then becomes an official sorority event, and the chapter will have to leave (or if they stay - they are running the risk).
Of course, this doesn't stop a lot of women, but this Resolution is there to help sororities make their members more comfortable at a fraternity house, particulary in social situations. (ie. no pressure to drink, mauling, etc. - you get the picture)
If you would like more information on this, visit the NPC website at
http://www.npcwomen.org or run a search on google on "Panhellenics" or "Greek Alcohol Policies" and many campus Panhellenics/Greek Affairs have their policies online - and some are even stricter than what NPC and these dry men have laid out.
Hope this helps!