i have a ps3 slim model (250gb) most games are quite laggy during cutscenes as well as gameplay its not the actual game, because I tested the same game, for example uncharted 2 on my friend's ps3 and it worked perfectly
(another thing, it is not the tv or hdmi cable, as i tested it at my friends house on his tv/hdmi cable) Also another reason i KNOW it is not the game, because most games lag despite being brand new. I tried to go get it fixed as i thought it was a blue ray problem but the person told me it wasn't, as if it were a blue ray problem, the game shouldn't work at all, not be laggy he said it was the first time he saw/heard about this happening, suprisingly with a slim model!
PS: my warranty is over a year now
(this problem was occuring even after jailbreaking) (i have tried a master reset/system restore/or whatever its called)
Even though it would not help with BD discs, try running games off the internal HD and see if they lag. If not, then it's definitely a fault with the BD laser or lens etc. If they DO lag, then something else is going wrong.
not too sure about the blue ray movies hey, don't have any so i'm assuming the games for now
i am running games through my internal hard drive, and it still lags (before and after the jailbreak, i thought the jailbreak would've improved the performance of the lags, it did not)
someone did suggest that it may be a burnt cpu (not sure if i heard right)
If your internal HD is set to SATA 2 then it WILL lag. Depending on the brand of your drive you may be able to find an application that forces your HD to work at SATA 1 settings. Goto the manufacturer's page for your HD and the application will be in the downloads section.