I just had this exact problem and wanted to contribute...
The solution offered above my GoDaddy worked beautifully. All of my tables were restored and my site is back up running. GoDaddy tech support offered a site security thing for $60/year, but I'm over them at this point. This is the second time this site has gone down and both times they were no help. I'll be switching this site over to Network Solutions. However, GoDaddy rant aside, I followed these steps exactly...
You mentioned that you found a table showing "in use" and that you got a message stating that the wp_posts table had crashed. There's a very simple way to fix this if you're already in phpMyAdmin:
If you're not already on the page where you see the tables listed, here's a reminder of how to get there. From the phpMyAdmin homepage, click on your database name on the left (there's probably two listed, "information_schema" and your database... don't mess with the information_schema on). It should display a list of all the WordPress tables, including the the one that shows as "in use". Once you're on that page, all you have to do is check the box next to the line for the table that is listed as "in use", and select the "Repair table" option from the drop-down window at the bottom of that page. phpMyAdmin will immediately perform that operation, and presuming there's no other failure, the page will refresh and the table will be in a normal status again.