Ok, try a repair on it.
REPAIR table w3t_Online
The server looks good on the specs, but it could be that your MySQL configuration needs some tuning. Can you tell me what version of MySQL you are currently running?
If the repair works on that table we can try converting it to a heap table (basically the table resides in memory instead of being written to a file). We're going to be doing this by default for version 7.1, but this will also work with earlier versions.
