Sync is currently experiencing problems

I had the same problem and it lasted for saveral days until I took the battery and sim card out and reinstalled them. It then came back up sync.
That solved it for me.

What this means is Google is probably updating their sync / Gmail somewhere dwn the line. not a major problem, give it an hour or so and it should be Ok !

I had the same problem and resolved it next way. First backed up all my contacts on G1 with myBackup, then deleted all my contacts on Google from laptop. Autosync all the time was on, so all contacts was deleted from my G1 also. After that I restarted the phone, and restored my contacts with myBackup. When my G1 tried to sync it asked me what to do, because it have too many items to delete (from "All contacts" category on Google). I've chose "delete". You may try other choice. After few minutes I've had exact all my contacts from G1 on Google no less, no more, and no sync error. Remember: just in case, backup all your contacts on G1 or Google before deleting them, to prevent them from beeing lost!! Good luck.

Wipe the phone. This will take all contacts off the G1. Go thru the whole process of entering your login info again and the contacts will sync from Google. That did it for me.