Strange,
you technically could get 2048x1530....
But i suppose that the cause is that something has eaten up the fast memory...
What else are you running?
(hehe, hopefully not Fblit with the card)
But i suppose that a dodgy memory module could `limit` the available screenmodes.
(Have you tried reducing the colours?)
And does it `crash` or simply go blank when you try the higher modes?
[Or have you disabled the on-board memory somehow?
]
checked here?
or here?