I'm 99% sure it has nothing to do with the cable distance, but if it's crossover or not. You will sometimes get a link light but it won't connect if it's got the wrong pinout. i.e. crossover or not. silverbulletcouk is right.
568a or 568b are both fine, just one is usually residential, and one is commercial, but as long as they're the same on both sides it doesn't matter. The Orange and green pair just swap between 568a and 568b, but the numbering is the same, i.e. 12356478 where 1/2 are a pair, 3/4 are a pair, 5/6 is a pair, and 7/8 is a pair. http://pinouts.ru/
is my favorite site for these things.