Did you find groupExpColl error in your Logs?
A collegue send me a trace of MOSS (ULS file) with the following error:
Localized resource for token 'groupExpColl' could not be found for file with path: "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\Template\Features\<CustomList>\schema.xml
And I realized we didn't include the DefaultResourceFile attribute. Sample: DefaultResourceFile="core"