hey there, Just wondering if 256x16 / 512x16 is a correct texture size...

As long as your dimentions are powers of 2 (they don''t have to be the same) there should be no problem.
(tried on my TNT2U -> worked fine)

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UNKNOWN caused an invalid page fault in module unknown at 0000:bff80eb6
: win98 with multiple sclerose

yes but not on all cards
eg voodoo1/2/3 cant handle textures with sizes bigger than 256
or a ratio larger than 8x1
eg 16x2 OK 32x2 NOT OK (on voodoo)

http://uk.geocities.com/sloppyturds/gotterdammerung.html