Hi Tim,
Without the complete set of steps you're using it's hard to know what you may be running into on this one.
Have you created a Network Installation Point for Office 2007?
What version of Windows?
What are the customizations you've made to the Config.xml (and which of the several folders for Office 2007 are you configuring).
Are you using Setup /Admin to access the Office 2007 Customization Tool (OCT2007) to create an Office Customization Patch (.MSP) and
setting the display level in that file?
http://officebeta.iponet.net/en-us/techcenter/HA101129741033.aspx?pid=CH100628601033
For corruption of the Config.xml files be sure you're following the conventions here
http://officebeta.iponet.net/en-us/techcenter/HA012306521033.aspx?pid=CH100644431033
To access the Officebeta. website you'll need to be on a computer with 2007 beta 2 or the ActiveX control from link #3 below
installed.
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I have tried to install Office 2007 beta using the xml file, but firstly I
cannot install it silently, will only install with basic ui, and seconldy if
I try and set feature states to Absent for say AccessFiles it says the xml
file is corrupt. >>
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I hope this helped you,
Bob Buckland ?

MS Office system products MVP
LINKS to the 2007 Office System
1. Read about it, try it, or watch the movie

the 2007 Microsoft Office system info,
online Test Drive, or downloadable beta is at
http://microsoft.com/office/preview
2. Already have 2007 Office System Beta 2?
Send Microsoft your feedback (with pictures)
http://sas.office.microsoft.com/
3. Use the 2007 OfficeOnline website without Office2007
a. Install the ActiveX access control
http://office.microsoft.com/search/redir.aspx?AssetID=XT101650581033
b. then visit
http://officebeta.iponet.net