Unknown Zone(Mixed) seems to be breaking Spell Check in OWA 2007

Where seeing an issue with a small amount of users - and handful out of 7000 migrated to 2k7 where spell check is not working in OWA. It also appears to only be occuring when users access OWA from within the corporate network. The only common denominator is - when a user clicks on "New" to create a new message in OWA - The zone changes from "Intranet" to "Unknown Zone(Mixed)". Trusted sites/zones are all handled via GPO here. Machines exhibiting the Unknown Zone(Mixed) issue have the same Group Policy applied that systems that work do (verified with GPResult). We were speculating that it may be a setting in IE 7 that isn't handled by policy but could not locate. OS is XP. Wrkstn DNS settings are consistent and a tracert to the OWA infrastrucure is consistent between 2 machines as well.
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You will need to edit the registry for each user.
Browse to this key. (be sure you are looking under HKEY_CURRENT_USER, not HKEY_LOCAL_MACHINE.

HKEY_CURRENT_USER\Software\Microsoft\Shared Tools\Proofing

Rename the "DLL" and "LEX" entries to oldDLL and oldLEX. They are probably pointing to non-existing files and will recreate correctly when office is restarted.

Close office and restart.   This should fix your issue.
Assuming this solution works for your particular problem, the registry change could be scripted and put into a login script, or given to users as a batch file or VB script they could each run to fix the problem under their individual profile.

BadFishTooAuthor Commented:
referenced Key does not exist in registry. Also - any user who logs on to machine exhibiting the problem also gets the "Unknown Zone(Mixed)"...which would kind of eliminate HKCU from the solution. But thanks so much for the input!
BadFishTooAuthor Commented:
Using Fiddler to capture IE traffic - we noticed that systems showing the "Unknown Zone(Mixed)" status have traffic to urs.microsoft.com:443. This site isn't in our trusted sites zone which is handled via GPO. We also have phishing filter enabled on the intranet and internet zones via GP. Any idea why one client would initiate traffic to this URL when generating a new message in OWA and another wouldn't (both have the same policy applied to them).
BadFishTooAuthor Commented:
Turns our Uknown Zone(Mixed) was a symptom of problem not Root Cause. It appears that S/Mime COntrol for OWA 2007 is breakig Spell Check. For some reason - after loading S/Mime Control - Unknown Zone(Mixed) shows - as well as spell check breaking. Closing this question and opening question regarding S/Mime COntrol Breaking Spell-Check

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