We have had issues with upgrading HIPS on our Solaris boxes as well, and it has been a pain getting some of them upgraded. I have found that it was just easiest to run a remove task from the ePO server, and when that doesn't work (which sometimes it wont) just uninstall manually, then re-install and push the new patch, which has worked for us.
To manually uninstall (disable the policy first if you can, and need to run as root):
/opt/McAfee/hip/install_hip_solaris -uninstall
Check these directories for logs and see if it has any indication of whats going on..
/opt/McAfee/hip
/opt/McAfee/etc/hip-install.log
