Dvd/cd burner dilema....only sees some media...its killing me

i have a problem thats driving me crazy. i have a liteon 1693s which has worked wonderfully since i got it ( 4 weeka ago) suddenly it chooses not to see certain disks but sees others.sees and boots from drive at start up.once in win 2000
it will see and read both bought and burned/backed-up dvd’s but will not write to dvd or cdr with nero or dvddecryter .doesnt see cd rom’s, will play music cd but will not allow to explore/view disk contents. it also sees some burned cd-r media but not others on same media brand.i have uninstalled
the device and updated/reinstalled drivers but not firmware.i am hesitant on this since i installed my previous cd burner (mitsumi) and it behaves in the exact same manner so that would be a fluke for both drives/firmware to fail.all i can think of that has occured between no problems and my currnet problem is i have found and removed a virus and tried installing dvdreadeasy (which failed to install correctly). when i click on either drive in 'my computer" i recieve an error "the disk in drive e is not formatted. do you want to format it now? yes/no. yes gets error “the disk in drive e cannot be formatted”.all looks right in device manager.could it be something during start up or int the registry?drive not seen in safe mode.any help is appreciated.thanks

Disable the IMAPI-Burn-Engine and only use proper burning apps like Nero.