SharePoint: "Failed to extract the cab file in the solution"

I'm receiving a "Failed to extract the cab file in the solution" error when I try to deploy my wsp using stsadm -o addsolution -filename... I've open the wsp as a cab and checked that there are no duplicate files in there as I understand that can sometimes cause this issue. The issue only started when I tried to include a custom field type as part of my solution, to do this I added the following to the ddf ..\CustomFields\ShortMonth\ShortMonthControl.ascx ..\CONTROLTEMPLATES\ShortMonthControl.ascx ..\CustomFields\ShortMonth\fldtypes_shortmonth.xml ..\XML\fldtypes_shortmonth.xml and `<TemplateFiles`> `<TemplateFile Location="CONTROLTEMPLATES\ShortMonthControl.ascx"/`> `<TemplateFile Location="XML\fldtypes_shortmonth.xml"/>` `</TemplateFiles>` to the manifest. I've tried taking it back to just references to the ascx in both but it doesn't see to help. Any ideas?