The first one sounds like either your drive is bad, or possibly the disc is bad. If it happens with multiple discs in exactly the same way, I'd think it's more likely the drive.
The second one involves streaming which is notoriously fickle and any number of ever changing variables can affect it. So, the first thing to do is try updating to Firefox 4 and assuming Netflix is using some kind of Flash system for streaming, upgrade that to 10.3 as well if you haven't already.
The PRAM just stores some settings like volume and mouse pointer speed, it would have nothing to do with this issue.
Something more cosmetic, but bugging me enough to post: when watching a DVD on my 17 MBP Core 2 Duo (3.06 GHz, SSD, 10.6.7), every minute or two or so, the video freezes for a fraction of a second while the sound goes uninterrupted. This happens with VLC and Quicktime. It also happens when streaming from Netflix using Firefox 3.6.17. However, it does NOT happen when streaming from Netflix when I use Safari.
Any idea what could cause this and how to fix it? I already zapped the pram...