Create Link Button Brings Up Blank White Window

This is a weird one that only shows up on some pages.

It's with WPMU 2.6.5

Write a new post and highlight a word, click on the link editor button and the little link window comes up but is just white and empty.

This member has other sites that are working fine.

This site was domained mapped but I removed them so it is sub-domain type site.

When the site was created, it did have mixed cased naming ie "Nautical-Stuff.maindomain.com" but having read stuff on how this can sometimes cause problems, I logged in as admin and changed all of the references to
"nautical-stuff.maindomain.com" but that made no difference.

If I remove domain mapping, logout, clear cache, login again, and I can post links again.

If I add a domain map WITHOUT logging out, the domain map shows and the link works again.

If i logout, clear the cache, login again, the links stop working :slight_frown:

I test in both FF and IE7.

Firefox gives no error, but IE7 gives the following error:
Line: 48
Char: 3
Error: 'this.params' is null or not an object
Code:0
URL: http://floridagatorXXXXXXXX.info/wp-includes/js/tinymce/themes/advanced/link.htm?mce_rdomain=mymasterXXXXXXdomain.com&ver=311

Anybody else handle (and hopefully solve) this problem?

..Mike