Sadly, despite its cost, Photoshop is not bulletproof and Adobe does not
address instability issues adequately--Bridge CS3 has always been a bugfest
and Bridge CS4 so far appears to be even worse (Bridge CS4 will never retain
settings for a custom desktop on my uber machine and I have tried
everything).
Problems like yours are usually not resolved by simple
uninstalling/reinstalling the program. Sometimes a search and destroy manual
sweep of your hard drive and registry to remove files and settings that are
not deleted by the uninstall routine will work (reboot before reinstalling).
Some other program/driver is usually preventing PS from launching due to
memory/resource conflict, incorrect dll version, or sloppy programming that
Microsoft has never cleared from Windows and is perpetuating in Win7/Vista
SP3. Adobe is as much to blame as Microsoft in the sloppy programming
department.
First: see if you have a system restore point prior to when the problem
developed and revert to that state. If that solves your problem you are
lucky as System Restore points, while great in theory, are often corrupted
or simply do not exist as they should.
Install the latest Video driver for your system. New video drivers cure many
ills.
Will Photoshop load if the antivirus/firewall program is turned off?
Do you know how to systematically shut down background processes to find
what might be conflicting with PS? I recommend starting with Itunes if it is
on your machine as Itunes and the other gunk Apple puts on your system are
astounding resource hogs even when the program is not actively running
You can also uninstall OS updates to see if that is causing the problem
although less likely.
Viruses and malware do not usually affect just one productivity program like
Photoshop, unless you are loading the program from a networked drive, but
running scans will not hurt. My recent sad experience with one employee's
computer was that the most highly touted programs failed to identify/clean
the virus/malware (hijacked web sites and would not let networked programs
load) and only a wipe of the hard drive/reinstallation solved the problem.