There seems to be a problem with automatic checkpointing in Maxcoin wallet (new feature in latest 0.9.2 update)...
If your wallet does not sync, you probably have the "Warning: checkpoint on different blockchain fork, contact developers to resolve the issue" error... By running 'enforcecheckpoint false' in the debug window your wallet will sync back, but it does not fix the underlying issue with checkpoints.

Follow-up here: https://github.com/Max-Coin/maxcoin/issues/44