If you have the files on your system backed up you may be okay. The actions you see in the panel are stored in a file called Actions panel.psp. It's location is as listed here:
If you quit Photoshop, recover the prior version of Actions panel.psp via TimeMachine or whatever, then relaunch Photoshop you should see your old actions.
Thanks for your reply, Noel. Much appreciated. I don't have a file called "Actions Panel.psp" at the location specified above (though your message and the kb article indicate I should), but I followed your procedure for a file called "Actions Palette.psp" (which I understand is the old name) and it worked perfectly. Have a great day and thanks again. Saved hours and hours of effort. Cheers!
Hm, come to think of it that may be a long-standing typo in the web documentation.
I just looked, mine's called Actions Palette.psp as well. You did the right thing.