Windows 7: win 7 & vista dual boot probs

Posted a few days ago with dual boot probs, thought i solved prob.

Here's my problem, i have vista 64bit install as main system and have just installed win 7 on other drive (e) everything installed fine. When restarted had dual boot screen options vista or win 7, loaded into win 7 playied around for bit and did't use it for a few days, as still using vista.

In the past few days was still getting dual boot options but not going into win 7 as was using vista. But today tried to selected win 7 and get this error:

Windows can not verify the digital signature for this file

FILE: \windows\system32\winload.exe

Status: 0xc0000428

(mentions something about temp disabling driver signature enforement)

I've tried booting up via win 7 disk to repair, it does check on win 7 drive and tells me to restart, strangely enough it boots into win 7 if selection option on boot manager screen and seems to work fine.

But upon next restart, get to boot manager and select win 7 and get the same error again as i mentioned above.

Can anyone give me any ideas as to why the winload.exe is giving me probs?

Benn