Graphical issue after upgrade to rc5

[koops]

I am getting the following graphical issue after an upgrade to rc5 (went to rc4 from rc3 before that).



My forum up top. SMF community at the bottom (correctly displaying the graphic).

If I check the actual referenced file I think it is /smf/Themes/default/images/theme/menu_gfx.png and that seems ok. I even re-uploaded it to be sure.
File permissions on it are correct as I can load it seperately in a browser window if I go directly to the link.

Koops

edit: I notice that it looks fine in ie8, chrome 9.0.597.107 but not in firefox 3.5.14

edit 2 : ISSUE HAS NOW RANDOMLY DISAPPEARED! spooky.

[CapadY]

It look likes Firebug in action :S

Using firefox with this applet ?