GXP bottom bracket knackered?

I've had a Sram GXP bottom bracket for about 10 months / 6000 miles which started to grind and creak so I took the cranks and bearing cups off of the bike to clean all the crap off. When I put it back on I noticed that as I tighten the crank bolt, the actual bottom bracket starts to seize and the cranks become really difficult to turn.
I know the GXP system has a bad reputation, is my particular problem a common one?

6000 miles..... i wouldn't complain if i got that much from one.
Truvativ ISIS was shit.
GXP was as shit, but you you could get at bearings and repack them with grease.
6000 miles ? way more than i ever managed, but i did get use them in wet weather.

Seize => the bearings are experienceing side load. Cups are further apart than the axle is expecting? Check they are properly in the frame. Invisible spacers?

Yeah exactly, when I rotate the cranks I don't hear any grinding caused by muck inside the actual bearings. Just a faint mechanical friction which would be consistent with side load. The thing is if I don't use a spacer there's sideways play in the cranks and if I do use a spacer I'm squeezing the bearings together. What am I doing wrong?

In GXP system the axle / crank clamp either side of the LHS bearing (this is what the 24-22mm step in the axle is for. The axle should be completely floating in the RHS bearing. So if the axle is wobbleing then the LHS bolt is not tight or the LHS bearing is shot.

Gxp is fine. 6k miles is good going.