found this while using the opt comm bits  on linux and winNT. not an issue on mac. 1. dropdown the File menu (need to use the mouse on linux). 2. hit the right arrow key. result: New Navigator Window is selected; this is expected. 3. hit the right arrow key again. this time the View menu drops down --the Edit menu was skipped. 4. this is where symptoms on linux and NT diverge: hit the right arrow key a 3rd time. results: on linux the Debug menu drops down (several skipped). on winNT, the File menu drops down (backwards). 5(a). on linux, hit the left key couple of times to go the other direction. result: browser hangs; various menus are rapidly redrawn (or, rather, redrawing the outline of various menus) over and over --had to kill seamonkey (went to a shell where i launched it and issued Ctrl+C while holding down left-mouse button). (b). on winNT, also hit the left key a couple of times. the browser also hangs, tho' i don't see the crazed redrawing as on linux. need to kill browser w/NT task manager.
i don't know the state of arrow navigation (in menus) for beta. i'm nominating this for beta1 --but lemme know what its status should be.
Oh yes, this should be PDT+. Oh yes.
This is totally PDT+. Checkin in a fix.
coolio. verified w/2000021808 opt comm bits in winNT and linux --no longer crashes...