Seagate HDD showing as 'write-protected' in Vista

So I just built a new Core i7 rig, and last night I put in one of my Seagate HDDs that I had been using for pure storage in another PC. As I was installing the HDD I noticed that I still had the jumper in that limits the transfer speed to 1.5Gb/s, and not 3.0Gb/s. So for the heck of it I removed the jumper since surely all of the SATA ports on my Gigabyte X58 mobo support SATA II.

But now, I am sometimes I am unable to write data to the HDD. And by 'sometimes' I mean that if I find myself unable to write to the drive, if I reboot the PC I will most likely be able to write data to it again until the next reboot. If the jumper was the culprit, I would assume that the drive would be protected at all times.

The only other things that have stood out about getting this HDD up and running are that when I was in Disk Management trying to change the drive letter for this drive, that option was grayed out. I had to close Disk Management, and then go back in and only then was the option available to me. Also, I just checked Device Manager and this drive is showing as a 'SCSI Disk Device' even though it is SATA.

Any thoughts on things to check? I didn't see anything in the BIOS. Thanks.

Even SeaTools is reporting this HDD as a SCSI even though it's not. I wonder if I need to plug it into one of the non-RAID SATA ports on the mobo.

Wish I had some advice, but all I can tell you is that I have the same problem with my Asus P5Q / E6750 setup. I found that disabling the hibernate option reduced the frequency of these events, but every now and then I boot up, try to install a piece of software, and get the "write-protected" error. My drive is an old IDE plugged inot a JMicron RAID port on the motherboard.