Update package problems for Product Package

We are currently having problems building the update package required for a Product Package. The update package contains over 1000 objects.
We have been having problems with build seeming to hang "Updating parent package TAM file gbrspec".
We suspected a corrupt TAM file, so have rebuilt a full package,
but already the update package has been updating the new parent for over 7 hours. Is there any way we can skip the updating of the parent package for this update package, because I don't see that this step is doing anything worthwhile, but is causing us alot of problems.
Any other ideas?
TIA

Package build finally finished (successfully)
Update of gbrspec took 10 hours.
Any one got any ideas if this can be got around for Product Package, as I don't see that the update of parent gbrspec acheives anything here.