So, I had to adjust my truss rod recently as some buzzing was developing on my Low E.

I just went to adjust the intonation and I ran out of wiggle room! The saddle on the G is all the way toward the back of the guitar, yet the G at the 12th fret is still sharp (barely). The B and the high E are really far back also, but the intonation is fine. The three wound strings seem ok.

Any ideas as to what would cause this? The saddles were in "normal" looking positions when the guitar was new.

Old strings maybe (there's not that old though)?

I would put the action at just about perfect (I don't go too low because I like sustain and tone) and there is no string buzz.

This is on a Gibson Classic Custom with the stock tune-o-matic.
Hmmm... I've never noticed it this bad before. I wonder if it's these M-Steel strings. I might have to go back to nickel.
If you have a Tune-o-matic style bridge you can turn the saddle around to give you that little extra. It's a fairly common thing to do. I had to do it on a Les Paul I used to own. Never had any problems with it. Also, I hope you're saving up for a fret job if you plan on using M-Steel strings for long. Steel strings are HORRIBLE on frets.