After installing the latest update, Opera simply won't start. I click on the tray icon, the desktop icon,and the start menu, but nothing works. I tried uninstalling and reinstalling. Nothing. I even installed an earlier version. Still nothing.
What's happening?

Nope. No processes left open.

I did too, back when this first started.

@asplode - I tried just double-clicking both the 'launcher' and 'opera' exe files in the opera folder. The debug file gets created in the opera folder. I also tried a right click and 'run as administrator.' Nothing works.
As I mentioned, I think it is an access problem, although I have no idea why it would happen now and not before. I have an administrator account, and my permissions say I have full control.
Sadly, it's back to Firefox.

Here's a copy of the debug log:
[0517/150240:FATAL:launcher.cc(274)] Failed running Opera.exe
[0517/150248:FATAL:launcher.cc(274)] Failed running Opera.exe
[0517/150320:FATAL:launcher.cc(274)] Failed running Opera.exe

I believe the first numbers are the time. The code 274 looks like the error code.

I give up. I have an administrator account; I've installed earlier versions. There's nothing more I can think of.
It's frustrating because I was a satisfied user before. Something changed between the last version and this one. It's probably in my computer since I can't even install the old version any more. I get a message saying I can't access the exe files (launcher and opera) but I have no idea how to fix this since I already have an administrator account.
Thanks for the suggestions anyhow.

Couldn't access prefetch folder, but removed every reference to Opera that I could find in the registry.
Same result, same debug message.
My user account shouldn't matter since I had successfully installed and run Opera before this.

asplode: I didn't attache the file. I just copied in the text: "[0516/132722:FATAL:launcher.cc(263)] Failed running Opera.exe"
I've also tried running the exe files as administrator. I've deleted, reinstalled, old version, new version. Absolutely nothing gets Opera to start, despite having used it successfully up until now.

Based on the error message I get when I try the exe file directly (can't execute the path or file; may not have appropriate permissions to access the file), I suspect it may have something to do with access control. I've tried giving full control to the Opera folder to all users ((creator owner" "system" "administrator" "trustedinstaller") but that didn't work.

I also did a complete uninstall and delete of all Opera files (appdata, local, roaming, etc) and then reinstalled, but same problem. I'm at a complete loss.

I deleted everything and tried reinstalling version 20. Even though I ran this version for several weeks, now it's the same result - it won't start.
Here's the debug file:
[0516/132722:FATAL:launcher.cc(263)] Failed running Opera.exe

Here's the debug log: Failed running Opera.exe
[0516/082556:FATAL:launcher.cc(274)] Failed running Opera.exe
[0516/082644:FATAL:launcher.cc(274)] Failed running Opera.exe
[0516/082657:FATAL:launcher.cc(274)] Failed running Opera.exe

I would do that if I could, but remember, I can't start Opera.

Windows 7, 32 bit. Intel i5, 2.6GHz.
I just ran the installation file again. No error messages. Same result - nothing happens when I click on any icon. I also tried starting the .exe file directly. I got an error message that says it can't execute the path or file, and that I may not have appropriate permissins to access the file. The thing is, it installed fine a few months ago and I had been using it until now.