SGS2 + CM9: Gmail Sync Not Working (Outgoing)

Read some emails in my phone this morning, then logged into web Gmail and noticed that those supposedly read email are still unread (as in bolded). Enabled/Disabled sync but still the same. Only outgoing sync wasn't working (delete email in phone but not reflected in the web version). Other Google Apps (Contacts, Calendar) seemed fine.

1. Flashed gapps-ics-20120429-signed.zip; Why? Because I started out with 20120422, and the recommended version is 20120317. Didn't work though, outgoing Gmail sync still isn't working.
2. Tried sending emails out and it gets stuck in the Outbox. What the heck is that about?
3. Since A LOT of issues can basically be solved by clearing/wiping/deleting something, I'd give it a try too.
4. Go to Settings > Apps > Gmail
5. Click on Clear cache, followed by Clear data
6. Run Gmail again, and outgoing sync is working again!

P.S. My next move would have been to reinstall Gmail again. LOL