Samsung cd-rw not seeing blanks - tried 'sticky' advice

Hi Freaks
Posted before but suspect I presented a confusing case so no response.
Samsung Combo SMS-348B gives 'No disk in drive' message when try to burn using XP (and previously Roxio EMC 7). Worked fine before AND will still burn OK to disks with some data on already!
Reads audio, game and data CD-Rs OK - latter after a long pause. Had Roxio 7 but stripped out all software using Roxizap after uninstall. Deleted cdr4-xp etc - registry entries placed there by Roxio as per a MS KB article too. Installed ASPI layer using ForceASPI.
Recording tab present in CD-ROM properties and checked box to 'record using this drive'. Deleted Upper and lower filters as per MS KB article from specified sub-key. Uninstalled driver and reinstalled umpteen times in Dev Manager. Same for secondary IDE where drive is.
Drive burns normally now when in my son's PC with no problem so not hardware at fault. No changes in hardware setup - cables etc.
Tried installing CDBurnerXP Pro but no dice there.
Has anyone got any ideas?

Hi
In case anyone else has a similar issue.
Samsung Combo CD-RW/DVD-ROM didn't recognise blanks in order to burn tho' it played audios, game CDs and burned to partially filled CD-Rs with some data on!

Tried all software fixes in 'sticky' - no good. Tried drive in son's PC - worked fine. So I thought 'Not a hardware issue'. Changed ribbon cable - no change. In despair I cleaned the lens with Isopropyl Alcohol by dismantling the drive. It didn't seem that dirty. Removed the odd hair also! Bang - it worked again! Strange that it worked in son's machine but not mine tho if due to a dirty lens? Could it be that his PSU was churning out more amps (mine is pathetic) and so the laser was more powerful and so could read the lower signal from a blank CD-R? Who knows?
So if no dice from anything you've tried don't take it as a foregone conclusion that its not a dirty lens or something even if it works just fine in another machine. Clean the lens! - carefully.