www.makemkv.com

I tried to convert a few dvd to mkv and the problem I am facing is the mkv file runs in vlc, and then crashes withing seconds, sometimes minutes, specially when I try to fast forward (Ctrl+right arrow) in vlc. And MPC just stutters.

What version of VLC do you use?

Sounds like your table or record, or whatever MKV calls it, that basically keeps a list of each frame and where they are in the file, is either currupt of non-existant, there's a command you can use with mmg.exe to create these, although it creates a whole new file, so you'll have to delete the original one (after testing it, of course.)

That list is used for fast-forwarding and rewinding btw.