wierd shifting with abs light on

[Jonmf]

Hi I dont post much since I never had any problems with my car until recently.
ok here goes ..
Anytime the anti lock brake light is on my car wont shift properly .. iE. driving from a stop il shift from 1st to second at around 3000ishrpms .When I push the clutch in the rpms will not drop until i let off the clutch the rpms stick for about 5 seconds then drop. This happens in every gear . If i shift lower in the rpms they will climb to 3000..... what makes it more confusing is that the car shifts fine when the anti lock light is off... ..........
car is a 91 TT with 145,201kms

-Jon