Drive letter now unusable - Please help

[Magnetar]

One of my drive letters has become unusable, and I don't know why.
I was able to access the three folders I had on that partition, but I was unable to access the first folder of the drive (enter the drive from My Computer, or any other way via Windows Explorer).

Luckily I was able to access those folders and back up all the data.
The other partitions on that HDD are fine.

After trying different formatting combos I tried labeling the partition with another drive letter (S instead of F) and it worked!
I copied everything back to the partition now labeled S: and it's been working fine.

I ran tests on the HDD (chkdsk, etc....) and the drive appear to be fine.

I can only conclude that there's something wrong in the OS as far as drive letters are concerned.
I would like to know how and why this happened, how I can prevent it (if you can), and it would be nice to have my drive letter back.

I've never ran into this before, and this build as been rock solid for almost a year now.
Spec: Vista x64 Ult SP2 fully updated.


Please help.
Thank you.

[KeepSix]

Have you been using any external USB drives? I've seen those bork drive letters occasionally.

[Magnetar]

I have been. Haven't seen that happen though.

[Magnetar]

Update:
I decided to test a few more things. I wanted to see if the issue still happens in safe mode, which is something I should have already done.
So, I changed the drive letter from S, to "the F". I didn't think It'd work or do anything new, but it did!
It now works fine... Crazy stuff!

I'll update this thread again if anything happens, or I learn anything new to add.
I'm not going to bother with the safe mode test for now since it's working and all.