The biggest obstacle to getting me back into the game right now has been the fact that all my characters had some of their powers and feats reset in the last couple of months. From reading other MMO blogs I've gathered that there are a fair number of people who enjoy trying out different builds and who love games that encourage them to do so frequently. For me it's the exact opposite though.
In my main game I can just about deal with having my talents reset, but in one I play more casually, like Neverwinter, having to re-assign points to abilities I can barely even remember becomes a huge obstacle to getting me back into the game. Fortunately I managed to sit down today and "get on with it" on all three of my characters. Even if my new builds are terrible (which they probably are), at least I can get back to playing.