My account has thousands of ETH in it, but MIST says this:
"We can't estimate your gas usage properly, as you need at least 1 ether in your account."
My Mist and geth are all updated to the latest versions.
Also my node always syncs to the latest block when opening Mist, but once Mist is open it stops syncing.
Best Answer
There is a bug in 0.7.2 (as well as some previous versions?) that seems to occur when you use the "send everything" function to send to a contract.
If you send everything but 0.1 ETH the transaction should go through.
There is a separate syncing bug that seems to be occurring quite frequently with Macs. Some people have had success with the following:
restarting computer
installing new version of geth
deleting chaindata folder and then using geth --fast to resync.
going back to Mist version 0.6.2.
Uninstalling all versions Mist and reinstalling (if you have like 0.6.2 and 0.7.2 both on your computer.