I'd look at the system eventlog.
If the freezes are IO timeouts (that's what it sounds like to me) there should be events for that listed to confirm your problem.
If the freezes were due to I/O timeouts I would expect the hard drive activity light to be lit. But yeah, this does sound a lot like an I/O problem.
To the OP: Have you tried replacing the SATA cable to the SSD? I'd start with that before flashing the firmware or replacing the SSD.
I've also seen this on my own desktop machine and wiping and reinstalling windows with the latest drivers fixed it. I later found out there was an issue with the driver for onboard sound causing a memory leak and the pause was the machine swapping to virtual memory. Since I had 8gig of ram and 12gig swap file I never got the out of memory error that other people were complaining about, just a pause of a minute or so with the HD's pegged.
Yes, I had a similar issue on my Ubuntu Linux box recently. System would freeze up for about 30 seconds and hammer the swap partition. I never did figure out exactly what the culprit was, but I suspect I had a buggy X Windows installation with a memory leak somewhere. Upgrading to a newer kernel and X Windows stack seems to have cured it...