Inspiron, probably a NEC burner which should be decent for the job. Browsing the web and running a torrent app will impact your burns quite a lot (the disk has to slow down whenever the processor is tied up doing something else, you want a uniform burn not one done with constantly changing disk speeds to get the best results), it's suggested you burn with nothing else running but the burning app and preferably on a clean reboot (and has been suggested since even PSx days.) These consoles are meant to read pressed disks, any variance in the data from pressed is going to impact readability - and these games aren't designed with those kind of faults in mind.
If I had to bet on it, you were clicking a link and loading a page with graphics on it at the exact time that sectors with files containing things like the text or video you are having problems with were being written, all while azerus was tieing up a percentage of cycles doing scrapes and making links to other PCs - but since I don't have to guess I'll just tell you this again - it comes down to you experimenting and finding out what works properly for you and your hardware.
Burning at 1x or 2x will not make a difference if your problem is the fact your PC is busy doing other things, and as I said, burning at a higher speed can make a far better burn sometimes. All else fails, you can tweak your 360 laser or get another and see if that makes the difference.