My virt-manager was working just fine and all of a sudden stopped working, throwing in error: RuntimeError: could not open display

root@rakcal ~]# echo $DISPLAY
localhost:10.0

[root@rakcal ~]# virt-manager 
Traceback (most recent call last):
  File "/usr/share/virt-manager/virt-manager.py", line 383, in <module>
    main()
  File "/usr/share/virt-manager/virt-manager.py", line 286, in main
    raise gtk_error
RuntimeError: could not open display

Has anyone seen this before? the same thing happen to "virt-viewer" as well:

[root@rakcal ~]# virt-viewer winxp1
Cannot open display: 
Run 'virt-viewer --help' to see a full list of available command line options

Does anyone know what might be the problem or if I'm missing anything? Reinstalling "virt-manager" didn't bring any good. Any help would be appreciated. Cheers!!