stsadm import gives FatalError: Value cannot be null. Parameter name: g

Hi,

I'm trying to move a subsite to a site collection by export/importing the site content in SharePoint 2007. I have done this a number of times without real issues. But this time I encountered an obstacle during the import and I can't find a solution for it. When I run an stsadm import command, I get this error:

[7/26/2012 11:58:18 AM]: Progress: Importing File Web Images/waitingonsomeone.png.
[7/26/2012 11:58:18 AM]: Progress: Importing File Web Images/XO.png.
[7/26/2012 11:58:18 AM]: Progress: Importing File Web Images/yellow.png.
[7/26/2012 11:58:18 AM]: FatalError: Value cannot be null.
Parameter name: g
   at System.Guid..ctor(String g)
   at Microsoft.SharePoint.Deployment.FieldTemplateSerializer.FixLookupFieldSchema(XmlNode fieldNode, Guid parentWebId, Guid fieldId)
   at Microsoft.SharePoint.Deployment.FieldTemplateSerializer.CreateField(SPWeb web, SerializationInfoHelper infoHelper)
   at Microsoft.SharePoint.Deployment.FieldTemplateSerializer.SetObjectData(Object obj, SerializationInfo info, StreamingContext context, ISurrogateSelector selector)
   at Microsoft.SharePoint.Deployment.XmlFormatter.ParseObject(Type objectType, Boolean isChildObject)
   at Microsoft.SharePoint.Deployment.XmlFormatter.DeserializeObject(Type objectType, Boolean isChildObject, DeploymentObject envelope)
   at Microsoft.SharePoint.Deployment.XmlFormatter.Deserialize(Stream serializationStream)
   at Microsoft.SharePoint.Deployment.ObjectSerializer.Deserialize(Stream serializationStream)
   at Microsoft.SharePoint.Deployment.ImportObjectManager.ProcessObject(XmlReader xmlReader)
   at Microsoft.SharePoint.Deployment.SPImport.DeserializeObjects()
   at Microsoft.SharePoint.Deployment.SPImport.Run()
[7/26/2012 11:58:19 AM]: Progress: Import Completed.


The import command I'm running is this:

stsadm -o import -url https://myUrl.com/sites/test -filename C:\restore\exportedContent -includedusersecurity -updateversions 2 -nofilecompression

The "FatalError: Value cannot be null. Parameter name: g" occurs right after "Importing File Web Images/yellow.png". Does this mean that the yellow.png was not found? If so, where do I check for the presence or absence of the image file? Please help!