Had this a couple of times, try going to Tools>Reset Blockchain and Transactions to reset them. You should see it start synchronizing.
There are actually official 32bit releases of Multibit. Go to
https://multibit.org/releases/multibit-hd/multibit-hd-0.3.0/ and choose the one without "x64".
Create a wallet on Multibit HD, keep a backup of the seeds and send all the coins from multibit classic to an address in MultiBit HD.