i had an issue that sounds like this as well where meat boy was constantly squishing on the ground, mainly in certain early warp zones. Supposedly you can fix that by using the detail launch options here http://supermeatboy.com/forum/index.php/topic,97.0.html
I was already using those just to make sure there werent any issues but i guess it ran to fast. It stopeed happening to me when i disabled -lowdetail options which i had previously enabled. (even ran fine for me on -highdetail)
Though i also hear controllers outside of the stock wired 360 one have compatibility issues so there is a decent chance it could be that too.