CD not holding more than 30MB!

Hi! I don't have my own computer so I use one at the University.Don't know anything about its specs but...here is the problem.I have pictures at my Yahoo briefcase account that I want to save more securely in writting them to a CD,using the CD burner in that computer.After saving 48 files,I got the message the disc is full and worst,on one attempt,46 of the files did disappear and one got corrupted leaving me with one BIG file!My pictures are all within 500 and 600 KB(coming from a small 1MP camera)and for each picture,an HTML link also get recorded which add about 500 bytes so...we talk here of 48 X 600.5 KB at the worst,which is less than 30 MB,and...the disc is full!In another occasion,on the same computer,I was scanning some pictures with a flatbed scanner,then uploading them to Photoshop and then saving them to the same CD burner.After I don't know how many files recorded(I would guess about 40)I got the message the disc was full and worst...all my files were gone!... and you can't record anything on it anymore.(I even try it in another computer and the computer don't even recognise it!)That CD was an Imation CD-RW 1X-4X.The two other who got jam after recording 48 pictures(one loosing almost all the files,the other one,keeping them)were Fujifilm CD-R.Do you have a clue was is the culprit.That computer is the only one available with a CD burner so I can't try to test elsewhere.Thanks.