I have a 2-year old Hitachi Progressive-Scan DVD player with problems.
Some discs (it seems to be worse with dirty or scratched ones) it won't
play at all- it can't find the disc. Others, it starts getting jerky
or freezing up partway through. I thought it might just be dirt on the
lens, but I tried cleaning it and the problem persists. Any thoughts?

BTW, my electronics proficiency is modest, so if this is something
difficult to fix, I'm probably chucking the unit.