I had the same! I tried this and it work's for me:
Thanks UJ, I tried changing the WiFi Connection's DNS setting to 8.8.8.8 and it worked like a charm! Steps followed:
1. Turned Off (hard "shut down") my iPad2.
2. Unplugged from PC.
3. Turned iPad2 back on.
4. Went to Settings > Wi-Fi > (my access point's setting by tapping on blue circle with white right arrow to the extreme right-hand side)
5. Tapped on DNS area, deleted what was there, and changed to 8.8.8.8
6. Closed
7. Did another hard shut down of iPad2.
8. Waited 5 minutes (don't know if this really did anything; I doubt it 🙂 )
9. Turned it back on and reconnected to PC via USB port
10. I noticed it automatically did a sync (dont' know if this means anything, but it didn't do it b4).
11. Voilá, it immediately started sending the messages that were pending.
Gr. Rick