Dear Lazywebs: Why does Firefox hate me?

Cross-posting this anywhere I can, because I'm clueless and this sucks. I am running Windows XP Pro SP3. I have used Firefox for years without incident. Yesterday, without apparent cause (no immediately precedent downloads or installations), the following symptoms began:

On opening a new window—either a new browser or any kind of dialog box—responsiveness to mouse and/or keyboard commands is impaired or completely absent. I.e., I cannot click on hyperlinks in a page, cannot click control buttons in toolbars or action buttons in dialog boxes, cannot click the close box at upper right; also cannot ALT-F4 to close the window. However, menus are generally selectable by mouse or shortcut in all cases. When I navigate (e.g., ALT-Tab) away from Firefox and then back again, responsiveness is restored, at least until the next time. Most recently, all mouse and keyboard functionality has been disappearing after a simple new-page navigation within the same browser window (even when only one window is open). For example, in MSN Hotmail, I switched from one email account to another; the new account's inbox loaded, but I could not click anywhere on the page.

Secondarily, earlier today I was composing an email on Yahoo mail and opened a second window to look up a fact. I struggled for a while with non-responsiveness in that second window, and when I went back to the first, MY UNFINISHED EMAIL HAD BEEN SENT. I have no idea what that's about, but Firefox somehow construed a click or ENTER command performed on ANOTHER BROWSER WINDOW. This is scary and unacceptable.

I disabled all add-ons (itself a nuisance because opening the "Maintain add-ons" window causes non-responsiveness every time). I have used "Add/Remove Programs" to uninstall Firefox and I reinstalled an earlier version (3.0.4) but the problem immediately recurred on opening a second window. I also tried updating the mouse drivers and using a brand new mouse.

I really like Firefox. It would be a great shame if I couldn't use it anymore. Whadayathink?

ETA: I am test-driving Google Chrome.

Firefox woes, part 2

I just spent an hour in a chat with a Firefox techie, who had a bunch of ideas that didnae work. Her/his final advice? Contact Dell support.

I ran a full AdAware scan (I've used AAW for years); it found a bunch of Privacy objects but no Critical Objects. The chat tech also recommended running 'hijackthis.exe'—which I did, but I dunno what to make of most of the output. Anybody here want to take a look?

One other strangeness that manifested: my mouse wheel was useless in Excel. Not Word, mind you, just Excel: the wheel would not scroll any spreadsheet. I have since rebooted (before you say it, Yes, I rebooted this morning when the Firefox problem first showed up) and, thus far, both Firefox and Excel problems have not recurred. Which is irksome in its own way, but not nearly so frustrating as the problems themselves.