Scanned through the posts here. I actually logged in today to see what experiences people had had with the ISRT caching and acceleration in computer builds made with Z68 chipsets and later.
Yesterday I decided it was time to clone my boot-disk HDD with Acronis. I always do so choosing to impart the same NT signature to the clone, and had previously been careful to delete the backup drive's partitions on a different computer. I forgot to do so this time, and in fumbling around -- made the source boot drive "unbootable." Turns out that Windows 7 fixes this problem easily, but I actually misinterpreted the messages Windows had given me as indicating a problem with the ISRT caching, when that wasn't the case.
When I finally restored "boot-ability" to the HDD, I re-activated the SSD caching, and everything was wonderful again.
So . oooo . . . I see the OP is using an SATA-II SSD for caching.
I've found that the best possible configuration for an Intel controller with both SATA-III and SATA-II ports is as follows. Get a 60GB SATA-III SSD with good specs (like a sequential read-rate above 500 MB/sec). I use a Patriot Pyro.
You only need to use an SATA-II HDD or an SATA-III HDD plugged to an SATA-II port. In process of configuring ISRT, hook up the SSD to an SATA-III port.
You'll gain little or nothing with an SATA-III HDD connected to either type of port. The gain derives from having an SATA-III SSD connected to an SATA-III port of the controller.
You short yourself using an SATA-II SSD, even though it offers a significant improvement over standalone HDD performance.
I'll be interested to hear about all types of experiences with ISRT from others, but this configuration of mine has been rock-stable. The only troubles I ever experienced occurred when I first built it and attempted to use a 128GB Intel Elm Crest for caching while using the remainder of its space as a formatted partition. The system would hiccup about once a week.
You're best to use a drive no bigger than the maximum cache size under ISRT. MY best understanding for latest-gen motherboards and ISRT: those which followed the Z68 (X79?) allow the use of larger caches -- perhaps with no limitation on the size of the SSD.