i had that weird problem after 1.09 patch 2 came out- i'd chase and chase a dot, never getting to con range, but not dumping for a long time either... it went away on it's own iirc, unless i fixed it by....
a) reinstalling dx8.1
b) reinstalled vid drivers
i can't really remember how/what why... but if reinstalling AH, or trying a/b above don't work.... it might just be the wonky connex lately.