Hi Senotark ,
Looking over this thread, great advice from other members and hopefully your burning problems are over… 
A few thoughts…
Your laptop specs are on the lower end, but still should do ok. This is not a criticism, please don’t take it that way. My point is that with marginal specs, you should try to maximize your system’s capabilities, especially when burning. I would disconnect from the internet, disable norton (it’s a resource hog), spysweeper and any other unnecessary apps that are running. I don’t think this is the specific problem here, but it’s tough to tell. My money is still on the media and your burner’s write strategy.
MATSHITA (panasonic) drives are horrible…again, not being critical of you…it’s what came in your laptop…very proprietary, lousy with media compatibility and lousy with support.
Fab even has a disclaimer about matshita, at least with v.2.xxx, which is what you’re using
Take a look at this thread, there’s a chance you can upgrade your firmware if it’s a sony oem (original equipment manufacturer):
http://club.cdfreaks.com/showthread.php?t=176922
(More on Matshita DVD-RAM UJ-841S:http://club.cdfreaks.com/showthread.php?t=180785)
Your hdd is probably crammed. How much free space do you have?
While defragging is essential maintenance, for you, it’s probably “critical”, based on your specs.
Last March, I posted the beginnings of a laundry list for troubleshooting and asking for help. It’s a little dated but it’s post #13 on mack’s thread:
For Help .
Anyway, take a look, some stuff has already been suggested here, but you may get some new ideas.
Definitely defrag, try to maximize your laptop’s “power”, stick with main movie mode for now. I’d also recommend that you try a RW (rewritable) disc. Many have speed ratings of 2X, 2.4X and will slow down your burn speed, plus less frustration cuz no more coasters…
You may need to do one or more of these “steps”.
Also, I didn’t find your model burner at videohelp.com, but I found it’s cousin…Panasonic UJ-845.
Interestingly, a fellow Canadian said, "…Not tolerate of cheap media. It hates Memorex and Maxell media, but loves Sony and Verbatim…"
Here’s the link
Let us know what happens.