EDIT: Bug turned out to only affect the display of values and has been fixed.
I recently tried out the blockchain.info wallet and found a nasty bug. Don't use it until this is fixed.
Here is the bug report I sent them
I put 73.13086 BTC in my blockchain.info wallet. When I decided to send money the blocks I was presented with to confirm didn't make sense. The figures didn't add up and some numbers were negative.
Sending 50 BTC from address A containing all my current bitcoins to B results in the following outputs (Y is what I believe to be your internal address):
B 7.05032704 (exactly 50 BTC mod 2^31 Satoshis)
Other transactions produce results consistent with signed 32-bit integer arithmetic. I've decided not to accept any of these transactions.