Eseries / Communicators :: E63 - Can't Install Or Uninstall Sis/sisx Apps?

I have a problem on my Nokia E63 in that if I try to install sis/sisx (in other words, Symbian) apps on my phone I get a message saying the file is corrupted, and then the installation is cancelled. If I try to uninstall any sis/sisx apps already installed, I get an error message saying, "Removing failed". The problem started for apparently no reason about 3 months after I bought the phone new, prior to which I had no problem installing/uninstalling sis/sisx apps. No problem with Java apps they install/uninstall with no difficulty -- I have verified that myself.How do I solve this problem? I have searched the discussions forums, but can't find exactly what I'm searching for.I want to soft reset the phone or reinstall the current firmware. The problem with reinstalling the firmware is that I see no option given in Nokia Suite to reinstall the current firmware. Anyone know then how to reinstall the firmware?Otherwise, my other option is to soft reset (*#7370#) (not a restore to factory settings). But I have a few questions before I do that. I understand a soft reset wipes the phone memory.1. Will a soft reset erase the apps which were on the phone when I bought it, namely QuickOffice, Adobe Reader 1.5, Nokia Maps, etc?2. Will a soft reset erase Qt off of the phone?Can any E63 owner who has performed a soft reset (not a factory settings restore) on it, verify whether Quickoffice, Realplayer, Adobe Reader, Qt, etc. were still intact and working afterwards?