DVD-ROM not reading DVDs properly

This DVD drive is on a laptop. It used to read fine, but then one day while I was playing some AVI off of it it started getting jerky. I go back to the AVIs that were playing just fine before and they too are jerky. Any type of video, on any type of disc be it DVD-Rs or pressed DVDs (the legal type?) nothing runs smooth any more. I can still copy data off the drive, it detects discs just fine, but playback stutters. What could be the problem?

I used MPC for AVIs and WinDVD for DVDs. OS is WinXP. Transfer Modes are all set for DMA if available.