Somehow my Windows 7 partially remapped a drive letter to another entity. It happened suddenly with some unexpected behavior. I noticed it when it could no longer connect to a network share. I removed the mapping and tried recreating with no success. The drive could not be deleted. Restarted, the drive is not mapped, yet it’s still not available. Started googling and came across this forum discussion.

The problem is related to non-active drives still reserving a letter. In my case there are 4 drive letters reserved for card reader. I am assuming the card reader takes first 4 available letters, somehow this letter was inialized after that, and it broke the config. Explorer was still thinking it points to a network location, while it was a card reader port instead. So it kept showing random errors.

You can use Folder Options / Hide Inactive Drives in Explorer or Total Commander to see inactive drives, and then remap through Computer Management / Disk Management.

This is the second time I am having this issue on Windows 7. First time I had to clean up the registry from some ghost shares.