FS9 - Ailerons inoperative after take-off

Hi all, I'v been flying the MD-11 since 2 good years now. Recently, i'm experiencing a bothering problem when i'm handflying the beast (this never happened before). This happens just after take-off. At 1500AGL, it's getting difficult for me to manually turn, as if the plane was too heavy or if controls were very weak. Also when i'm checking on the flight control display, i can see the ailerons are moving without any smooth, like stutter effect, and even not going to the full ailerons movement (which is not the case when i'm on ground for instance). This problem doesn't occur when i fly another plane (so it's not my yoke settings apparently). Finally, i'd like to say i didn't change anything in FS, and that i'm configuring the MD-11 (take of data, fuel etc.) exactly as i always did. I hope my english is not too bad so you guys can understand my problem. Thanks in advance for your help. Nicolas RICHARD