I thought that might be to which you were referring . The mouse sensitivity in Witcher 1 is definitely a problem for some people , myself included when i first started playing it in 09 and especially on smaller monitors but after eventually getting a 23 in. monitor and
1680 X 1050 didn`t seem to be as bad but that may be just my perception . I don`t know what resolution you`re playing at but try to go as high as possible to see if it makes any difference .