Not an expert, but FWIW it sounds like Win7 is arguing with Ubuntu files.
You don’t say which discs contain which OS…except the Win7 you said was on a separate HDD…is that the same one with Ubuntu?
Does Ubuntu load OK and it’s only when this WD disc is accessed it fails under Win7 but not under Ububntu.
Dual booting may be the issue, as I understand you have to install Win first then the dual-boot program. However a Ubuntu Forum may be better placed as these things work their way through. IMHO, Win7 has a lot of issues, once away from the norm.
Have you tried a blank HDD in place of the WD? That should prove it not the connection/load, rather it’s what’s on the disc, or its format, etc.
It’s odd you say it took approx. 1-hour to return to failure…is this a [B]power-supply /B problem which even new drivers couldn’t fully fix…and is this 1-hour repeatable…software faults should be repeatable from a given “start” point.
Finally, is this problem recent, or ever since you attached just that WD.