folder naming

Hi all, haven't been on the site for a while, but something happened this pm that's left me perplexed. I have been downloading music from cds on to my desktop, creating folders for them and then naming them after the artist. Now, for some reason, I cannot name a folder or change the name of an existing folder or file. When I click on the field, the field changes (the text goes blue), appearing to allow me to change the text, but nope, it simply won't allow me to change anything. It's as if I have hit a key lock of some sort. I've checked 'Get info', all the permission are as they should be. There must be a simple explanation but I'm baffled. Any help would be much appreciated, it's ridiculous really. I've been using macs for years but never had this issue before.

Have you restarted?
Sometimes that will fix things, although it doesn't tell you why it happened.
A possibility is that the Finder plist file is corrupt.