Hi Martin,
I had some issues with 3rd Party Updates in the past, some similar to yours, and I found out that the best way to deploy 3rd Party Updates is to: first download them, then upload (publish) them from Software Publishing.
My advice for you is to delete the package from your WSUS server (both of them - original and your copy) and wait for the WSUS servers to replicate. Then from Software Publishing just download content first and then publish. Try to approve the package only to a short subset of computers first and see what happens...
If you need more help, just buzz...