No evidence. Mostly it's just a cache/reload issue. It's just simple to clear out everything while in your in options. However, sometimes cookies cause strange erros, like in Internet explorer sometimes webmail will go all black - black background with black text - the cookie webmail sets has gotten messed up and isn't calling in the css properly. So you clear out cache, cookies, and history and log into webmail again and it work.
And perhaps there is some kind of a page error for your stats that one browser is picking up and the other not. Possibly support could clear out the current files and force a regeneration of stats and stats pages? Just a guess though - I don't know how stats goes about updating the info.