Can't save any files in Xcode due to permission error

I suddenly can't save any files in any of my Xcode projects in my home directory. Not sure what caused this. Here's the error I'm receiving:

enter image description here

I don't think Xcode is correct, since I am the owner of -- and have read+write permissions on -- the affected files.

A few other fun facts:

I can edit these files in other applications as the same user, so the problem seems to be specific to Xcode.
Other users can create and edit projects in their home directory without issue.
Running Xcode as root (via sudo /Developer/Applications/Xcode.app/Contents/MacOS/Xcode) does allow me to edit these files.
chown, chmod -R 755, etc. on the directory containing my projects doesn't help.
Disk Utility > Repair Permissions doesn't help.
Reinstalling Xcode, clearing Xcode .plists, etc. doesn't help. Failing both on Xcode 4.1 and 4.2.

Thoughts? Hopefully I'm just missing something simple.

Solution

Looks like I had netbiosd blocked in my firewall configuration. After unblocking it and restarting my computer, the issue seems to be resolved.