SATA SSD + RAID

Hi all, I've inherited a system which has an Adaptec 2420SA RAID controller and 4x SSDs running in RAID6. There's no end to problems experienced with this setup; a disk seems to time out and get ejected from the controller at least every week. It's not always the same disk though, and I've tried replacing each of the SSDs with their spares, to no avail. Is there any known issue with using SSDs in hardware RAID that I've overlooked? Performance isn't *that* much of an issue, since it's only running Apache + mod_perl and a ~100GB MySQL database. Any thoughts appreciated Thanks, Hannah