You should look at the "DVD open and closes" thread on the General Harware forum (sorry can't post the link myself) about how a seemingly dead Samsung DVD drive in a Crystal Xbox v.1.6 was restored back to life. The laser carriage had stuck and before that happened it had similar symtoms to those described here.
If you need to clean the lens, try using a photographers negative/lens blower brush but without touching it with the brush. initially at least. Don't use aerosol air or anything similar - it probably wouldn't do any harm but it is far more powerful than necessary and comes with the risk of spraying the lens surface and the circuit boards with liqiud aersol propellant. Not a good idea.
A DIY alternative I used in my photographic darkroom days is any flexible plastic bottle with a narrow aperture cap and a length of drink straw attached. An old washing up liquid bottle is ideal, empty, thoroughly cleaned and dried of course, This will generate a controllable blast of directed air but not enough to do any damage. Unless the 'dust' is sticky due to moisture or whatever it should blow it off the laser lens or anywhere else in the machine.
I run a hand-held vacuum cleaner over (and I do mean over not touching) whenever I open up anything old and electrical to suck up any loose dust before and after whatever else I'm doing.
The point is not to touch the lens except as a last resort and certainly don't use any lens cleaning solution on it.
However, if you do need to touch the lens said photographic brush is suitable but any totally unused soft haired (badger/sable) artists brush should be OK too. For stubborn marks I'd use a brush as described but with a anti-static, lintless lens cleaning tissue wrapped around it. Be gentle.
This is an ultra cautious approach, you may well get away with a far less pedantic cleaning method but that's up to you to take the risk.
This post has been edited by fallenangle: Nov 19 2010, 12:42 AM