Tom - I've had similar problems with writers - you write a disc on F, but it won't read on G. Another time it can only be read on the drive it was created on. Sometimes works on another machine, sometimes not. 

I've used expensive branded media and the disc hasn't lasted a year - yet theres no brand discs in my collection over 10 years old (when they cost 5 quid each and a bad burn was a BAD thing!).

My strategy is to mirror files onto another PC.  Also make a working CD copy which lives near the machine (DVD's are OK - but when screws up you lose more data in 1 hit). Make a master copy - check that on both drives on the 2 machines - now file it safely in an zippable archive quality disc wallet - put that in another room.  

If you work from home - keep a copy a important files like customer databases elsewhere - somewhere safe - say with a friend you can trust.  I've helped run a few shops and occsaionally someone will misplace a disc - normally  when the tax  returns are due!

For favourite pictures - get them printed at a decent lab. Always be nice to the person who prints your stuff as well!

Sounds paranoid - but when you meet someone (like my neighbour) who've just lost all their baby photos to a system crash, or recovered photos for someone who's just lost a realtive.   

Pinky - you left the lens cap of your mind on again.