About a year ago there was a thread http://en.community.dell.com/support-forums/disk-drives/f/3534/p/19435058/20045470.aspx about a user with an XPS 9000/435T with a RAID0 array getting the "One or more disks is locked" message at bootup. I had this happen to me today, with my XPS9000/435T also with a RAID0 array, but from a very surprising source.
I've done several upgrades to my system since I bought it and up until now, I haven't had any major problems. I went to 24Gb RAM, added a new Corsair 850AX PSU, and installed an EVGA GTX660SC video card. The video card has been fairly unstable when gaming so I RMA'ed it from EVGA. I got the replacement card from EVGA today, and when I installed it, I got the "Disks Locked" error message at bootup.. When this happened, I could not even boot into the system BIOS or the RAID controller. I put the old video card back in and the system booted fine. I swapped cards several times to verify the problem and sure enough, it was a reproducible error. Each time the new video card was installed the system would not boot and gave the "Drives locked" error message. When the old card was installed the system would boot fine.
To my mind, there are only a couple of possibilities for this scenario.
1. The replacement card is defective.
2. There has been some modification to the new card, such that it will not co-exist with the MOBO or the RAID controller. The new card has a video BIOS version one minor rev. up from the old one. Support at EVGA tells me that changes to the video BIOS should not have any effect on compatibility with the MOBO or the RAID controller. Nevertheless, the new card will not work, the old one does, although it is still unstable when gaming.
So for now, the system is running with the old card. EVGA is shipping me another replacement card. I'll try it when it arrives and see what happens. Just goes to show that error messages can be incredibly misleading at times.