I'd be tempted at this point to nuke my $HOME/mgc/install.ixl folder and re-install the Mentor Graphics Installation Program (run install.ixl from the installation source again). I'd also delete the existing /eda/mentor/expedition directory or rename it. If no joy, then I'd look at permissions on the files that are being created and see if they look right considering your umask settings. You could try installing from a different Linux box or try launching from a different shell. If it still fails after all that, you may just want to open a service request. It could get ugly.
Mentor Graphics Customer Support
Removing the $HOME/mgc/install.ixl folder, re-installing the Mentor
Graphics Installation Program and running install.ixl from the installation
source again solved the problem.