Ubuntu 7.04 doesn't like my Adata memory, XP and 8.04 OK with it

[dfklink]

I recently decided to add some more memory to my system which is running Ubunut 7.04 64bit. I bought some Adata sticks 2x2gb =4GB total. When I put the memory in and tried to boot to my Ubuntu 7.04 it continually reboots and never reaches the login screen (the motherboard correctly recognises the 4GB). I am replacing 2x1gb =2gb of Corsair memory. When I put the Corsair memory back in all is well again. I updated my BIOS even though it does not seem to be a motherboard problem. There are no error codes or beeps. Interestingly when I boots to Windows XP with the exact same hardware, XP has no problem and boots right up. Also Ubuntu 8.04 32bit installs and runs with no problems. The problem seems to be in the 7.04 OS. I do plan to move to 8.04 64bit, but I am not ready to do that right now. I have no idea where to start. I have googled the problem and don't seem to come up with any similar issues, and I don't see anything on these forums that might help. Anybody out there had a similar problem or suggestions of things to try. My system:

Intel Core 2 Q6600
Gigabyte P35 DSR3 rev 1.0 BIOS version 12
Adata 4GB (used to have Corsair 2GB)
WD 75 GB 10,000 RPM drive
Nvidia 8600GT
Ubuntu 7.04 64bit all updates installed - dual boot to Windows XP

Thanks for any help.