T400 Keyboard Swap = frozen bootup screen?

[mh9162013]

I have two T400 laptops and they're both in fairly bad shape cosmetically, but still work just fine. One of them has more RAM and a better CPU (Running Windows 7 Pro), but a keyboard that's missing a few keys. The other has a complete keyboard, but less RAM and a weaker CPU (Running Vista Business). I decided to swap keyboards, but now the T400 with a better CPU and more RAM (and now a complete keyboard) won't boot up past the "Welcome" splash screen, where it seems to be stuck/frozen. However, the T400 running Vista Business and the incomplete kayboard boots up just fine (and the keyboard works just fine, too).

Is there something obvious I'm doing wrong or that I missed on the T400 running Windows 7 Pro?

[RealBlackStuff]

Maybe there is some dirt in the keyboard socket or plug?

[mh9162013]

Maybe there is some dirt in the keyboard socket or plug?

That's the only thing I can think of. But before I open up the T400 again, I wanted to make sure there wasn't a known compatibility issue or potential software cause.

[TPFanatic]

Im curious what you might see if you press Escape at the thinkpad splash screen, it should show diagnostics info, see if it’s getting stuck on something. The memory test can take awhile. On my p71 there is no way to see the memtest live so i just have to stare disconcertingly at a black screen for a minute while it checks 64gb. At least a t400 maxes at 8gb

[mh9162013]

Im curious what you might see if you press Escape at the thinkpad splash screen, it should show diagnostics info, see if it’s getting stuck on something. The memory test can take awhile. On my p71 there is no way to see the memtest live so i just have to stare disconcertingly at a black screen for a minute while it checks 64gb. At least a t400 maxes at 8gb

When I pressed ESC during the ThinkPad splash screen, it seemed like it went into some diagnostic mode, but it only last a few seconds and nothing stayed on the screen very long. Then it said there was an error in the previou shutdown and asked if I wanted to startup normally or in various Safe Mode options. When I tried to boot up normally, nothing happened besides the frozen Welcome screen. But when I tried to boot up in Safe Mode, it booted up. The trackpad and keyboard worked, too.

Any ideas on what sort of diagnostic tests I should run once in Safe Mode?

EDIT: When I went to control panel, nothing seemed unusual, although under "Other Devices," the PCI Serial Port and PCI Simple Communications Controller had the yellow symbol indicating no drivers were installed. Not sure this should lead to a freeze during boot up though, right?

Second update: When restarting from Safe Mode, it booted up just fine. Not sure what I did to fix it, but I'll take it.