DATA loss with SATA 3 Drive on SATA 2 Controllers?

Hello,
I've seen some very serious DATA loss with Seagate SATA3 drives on DFI and ASUS 775LGA Mobo's... Loss that is so severe that it is basically irretrievable. I've seen many others who state that it's OK to use the SATA 3 (6/gbs) speeds on these SATA 2 controllers, but so far, this hasn't worked for me on 4 different mobo's.. Should I just be jumping the drives back to SATA 1.5 speeds and call it a day? Is there any added benefit to the $40.00 PCI SATA 3 raid cards (such as bytecc)?
Cheers,

You may have some bad luck with you drives and motherboards. I have both sata3 SSD's and regular sata3 hdd's pluged into both sata3 and sata2 with no side effects. I needed an eaxtra two sata3 ports on my motherboard so I got this pci-e card and it does work for only $22.

http://www.newegg.com/Product/Prod [...] i-e%20card