Members Unable to edit their Profiles under Chrome + Other Browsers

Okay so we've got a problem where over the last two months about half our members cannot update their Profiles.

Instead of getting "Profile Updated" when they hit save, they get
"Invalid Parameter Detected at the above address: http://wizardswb.forumotion.com/profile"

It is a per-account problem, and happens regardless of what group, permission, browser, os and how long ago the account was registered.

I have one member who cannot update any of her accounts registered under Windows 7, Chrome, Firefox 4 or IE 8 (however her Admin account has no issues)
one who so far has no problems on anything and uses OSX and Safari
one who gets the error on one account under Firefox 4 on Windows XP
Myself who gets the error on only one account under both Windows 7 and Ubuntu Linux using either Chrome or Firefox. Yet all my other accounts registered around the same time, with same permissions on the same browser/computer have no problems at all.

No profile templates have been modified, and we're using phpbb2.

Anyone wanting a test account to have a look I'm happy to pm the password.

Images of error under Ubuntu-Linux running Chrome and Firefox.

Account working under Chrome:


Identical Account with Error under Chrome:


Identical Account showing Error under Firefox:

Try clearing your cookies and caches.

*sigh* if you read the post I clearly stated it happens on numerous computers and at least 4 different web browsers.

The fact that using the same computer and browser yet having different results with 2 otherwise identical accounts means that cookies/cache has nothing to do with it.