Enter/Return from the Search Bar doesn't work?

Running Firefox 1.5 (20051111) on my iBook (OS X version 10.4.3) -- I'm
new to Mac, so this may just be an OS X thing that I'm not hip to,
but... when I click in to the Firefox search bar or hit Apple-K to move
the cursor there, I can type in my query. When I hit enter to execute
the search, however, nothing happens. The cursor stays in the search
bar, and no search is initiated. Any thoughts? I've also tried
combinations like Alt-Enter, Apple-Enter, Ctrl-Enter, and nothing.

Thanks,

WPTunes