I'd actually argue that because Gallup has been doing something for so long that they're more likely to be worse at it.
Slower to change with the changing dynamics. Happens all the time in the business world (blockbuster, borders, etc). And technology has really changed polling.
RAND is supposed to show a more stable race because it polls the same people. But the trends should play out similarly regardless. And it has. Reuters, TIPPS, and Ras has had similar trends with RAND in the middle (it was a 2 point shit until today).
The non-trackers also show a similar result. If we look at things like Pew and other polls from a week ago to the polls today despite being different firms we're now seeing Obama +1 or +3 which does also signal the same 3-6 point shift back.
To me, the only polling firm completely inconsistent with the rest is Gallup right now. And we've seen their crosstabs by region to make us worry about what is going on. Hell, does anyone believe Obama is losing the entire South by 22 (including Florida)? I sure as hell don't.
Like I said, I don't know why this is happening with Gallup right now but it is. So either they are on to something and everyone else is wrong or it might be time for a shake-up in their firm.
edit: And don't think for a second Gallup isn't aware. They're probably looking at the other polls and trying to figure out why theirs is so different.