Right , its what I thought, its UDF format ( or packet writing) and its typical for a cockup that happens when adding more and more files. You've learned the hard way NOT to save CDRWs that way, you would be advised to leave it alone.
Don't try saving any more pics to the CDRW , it will make the problem worse.
Treat a CDRW as a re-recordable medium, not a hard drive or USB stick. Get two , they are cheap enough and when you want to add extra images , burn them from disc 1 to disc2 with the extra images included in the new burn.
Once you are sure they are there , then wipe disc 1 and repeat next time.
Make sure 'verify' is turned on in the burning software ( if thats what you are using ), and burn them slowly - like 4x - even if the disc is capable of more . Burns at low speed are much much much more reliable, and your images are valuable. Even better is forget the CDRW format and stick with CDRs or DVD's and save them as single session ( not multisession ) discs.
If you are short of hard drive space , and thats why you are burning them to CDRW, get a 4GB USB stick instead, but then be careful because they can be erased , edited . deleted etc , Write protect the files after adding to the stick as a bit of a precaution, FORMAT will over-ride that of course.
What software are you using to burn the CDRW , or is it the native Windows XP ( or later) attempt at it. How you recover the images depends on what you have been using so far.