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.