I would suspect a reflectivity issue, i.e. the reflectivity of burned versus pressed discs. Have you checked the media ID (MID) of the blanks you're using with something like Nero CD/DVD Speed, DVDinfoPro, etc? Brand means nothing, you want to know the actual manufacturer. Then check that against the lists at, say CDFreaks. You may just have crap media.
http://club.cdfreaks.com/forumdisplay.php?f=77
Difference in reflectivity can also mean that the laser lens may get just dirty enough to prevent play of a burned disc, but not a pressed one.
Nevertheless, you may already have ruled that out.
Have you tried uninstalling/re-installing MM? As to shareware burning apps, most do an adequate job. There are a few free ones that have a good reputation. CDBurnerXPpro is one, so it'll cost you nothing to try it, get it here:
http://www.cdburnerxp.se/
Good luck. BTW, I'm using RecordNow presently, and have used Nero a good bit (IMO, it suffers from bloat).