Mouselook stops at 90 degree

[Altairzq]

Hello, I just installed P1999, and I have only a little problem, when I pan horizontally in first person view, mouselook seems to work only up to a certain angle, about 90 degrees. Then it stops and i have to lift the mouse and put it down again to be able to continue looking around. It's not sluggish, it just stops like it was blocked for some reason. Anyone know this issue and if there is a solution? I'm using a Mac with Wineskin.