popgate2 was failing w/ cannot contact server 400+ errors
I switched to popgate and now it's not pulling my mail.

My popgate2 setup currently has no errors and I have not had any issues with messages getting stuck at Yahoo in over a month.

We have seen times when simply re-saving your current config will get mail flowing again. It is often an account specific issue, though system wide problems have also been seen.

For those of you directly POPping Yahoo mail... this message I recently found on the Yahoo blog may be for you:

http://feeds.feedburner.com/~r/ymailblog/~3/308403149/

Basically, they are having major problems with the recent rollout of new features (including SSL) and are rolling back the features.