from another thread:
0.3.20.1 -maxsendbuffer was too small for the initial block download-- you were probably just unlucky and connected to a 0.3.20.1 node. Connect to somebody running either 0.3.20.2 or an earlier release and you won't run into that problem (does bitcoinj re-connect if disconnected during block download?)
I'm running 0.3.20.1 beta. How do I upgrade (and keep my wallet and settings).
I could just try re-installing but I'm being cautious due to coins in my wallet.
I'm not sure about the (Windows?) installer, as I simply unzip and go (Linux). However, as far as I understand it the application and the wallet are only connected in as much as the application assumes the wallet will be a given location (unless you tell it otherwise). So if you install a new version of the client it should just work fine with the existing wallet.
Best bet, obviously, would be to back up your wallet before installing, and if anything goes wrong roll back to the previous version of the client and restore the wallet from your backup.
