Weakening Laser, Poor DVD Media, or the Game Itself?

[Geoduck]

I just bought a copy of Star Ocean: Till the End of Time, and had my neighbor burn me a backup on his PC (I'm a computer klutz, I confess ).

The game itself plays fine, but I noticed some inconsistencies with the load time. Most times, it loads from screen to screen (ie. from the shop to the streets) at an average of 2 seconds. But in some rare cases, (1 in every 30-40 loads, approx.), it took up to 20 seconds--in a few even rarer cases, the "loading from disc" dialog box actually came up.

I heard something about not exposing the disc's surface to light, which is something I did before discovering that I shouldn't (placed the DVD-R under the hot light of a tablelamp while cleaning it--dumb of me ).

In short, is the problem due to:

1) a weakening laser (probably not--about a year old, minimal to average usage)

2) poor DVD-R quality--shouldn't be, since he burned it on a Ritek RiData, I think (can't refer to the DVD-R, since I'm using a PC from an internet cafe right now). However, I did see some hairline scratches on it.

3) my thoughtlessness of placing a DVD-R under the light of a hot bulb
(albeit for less than a minute)

4) the game itself has loading inconsistencies (anyone who's played the game, please reply)

Thanks in advance!