Well, therein lies the tricky part, and at this point, I think you'd be best getting some help from Support at Symantec.
In the SIM, you can modify the settings to use the local PL file so you don't have to do an update to the installer. Even if you DO the upgrade though, you simply highlight the product that is installed and you can repair it.
if the Reconfigure is failing, then you have to look to LogViewer to find out why. Support has run into installation and console issues a lot, and while looking at the system, it's generally not too hard to find something that is out of place once you know what working systems look like. It's much harder though to do that based on what is a very generic "error" like you are seeing. via email.
Were I you, my next stop would be logs, but frankly, I'd also be looking at environment.
Why?
Everyone comes back and does this: It was working fine one day, and then the next day it was suddenly broken. A tech then asks - well, what changed? When the reply comes back "Nothing", we know someone is lying or uninformed. Something changed. MOST of the time, we run into GPO's and such that screw things up. For instance, a GPO that changes IIS settings, or modifies login accounts, or stuff like this.
You'll probably have to look for what changed, look at the logs, or something like that.
Again, GL. Sorry we've not been able to diagnose it right-off. These are not quite so simple of issues to find often.