Have you tried quitting and restarting? I've found in my testing that sometimes the client seems to become fixated with peers on the older chain, which means the sync will never advance. Seems it's a bit like pot luck when starting up; occasionally it takes a few tries. (Deleting peers.dat may also help - it will re-add the two seed nodes at next startup). As more v1.0 clients upgrade to the new version (and others join for the first time with v1.1/v1.2) this should become less of an issue. It is annoying - if it does continue I can always add code which will deliberately ignore the older clients. I'm trying not to segregate the network (since v1.0 clients can still use the newer chain) but it may have to come to that.