Extremely slow Disk IO, unresponsive VM

My VM started performing extremely slow, but CPU utilization is near 0. Anything that requires disk access is slow, like right clicking a file, it takes 30 seconds to bring up the context menu. It takes 10 minutes to zip a handful of php and javascript files. I tried restarting the VM, which resulted in an error (after 10 minutes of the Portal saying "restarting..."). It then inexplicitly said "Starting", even though it failed to restart. After it booted up and I logged in everything looked good for about 10 minutes and now I'm right back an unusable system.