What causes lipsync to go off?

[Frosty5F10]

I have created a couple dvd's that worked fine, but one of mine for some reason the lipsync goes off like halfway during the movie, just all the sudden. Also now I'm trying to burn a movie to dvd and it works great for about a min, then you notice a slight pause (very small) & all the sudden the sound sync is off by several secs.
I know that the mpg files on my computer don't have this problem, sound works fine, only seems to occur when authoring, is there possibly something causing it to go off that has to do with my hardware when burning?
I have a home built athlon xp 2600, 512 ram, SB audigy, AIW Radeon 9700pro, 120 gig 7200 hd, 4x sony dvdr+- drive.
nothing is running to my knowledge when this happens, except for the authoring program, the 1st time it happened I was using a diff program & even had 768mb ram.
any ideas as to why, I'm sure someone knows why.
thanks

[redwudz]

If you picture the audio and video as running side by side in a video file, you can see that if one or the other has a pause or a blank spot, the sync will change. Editing can cause sync change and errors in either file can do it. A computer is more tolerant of sync error and you may not notice the problems until you play in a settop box. There are many, many threads here on audio/video sync problems. If the problem is just in certain files, there is probably an error in that file. Authoring shouldn't cause sync problems in a good file.

[Frosty5F10]

is there any program that searches a movie for errors BEFORE you burn?
kinda expensive not knowing if the movie is gonna work or not, $2 a pop.
it goes off in a diff place than I edited too, I guess it messed up when resaving the file?

[Hardcoreruss]

Virtualdub can check for errors

[Shudder]

vdub can check mpg2 for errors? Didn't know that.

But you should check your source with vdub first at any rate.

And Media Player Classic can play DVD vob files right off the hard drive BEFORE you burn, so you can at least see if the vob is cool. If there's no error there then chances are it's your burner/burning software.