recent ISO's to CD do not boot

[George Hein]

Recent downloads of ISO's to CD from Debian and Ubuntu do not boot.  Recent Knoppix CD created and booted OK.  

I never had this problem before.  Using an HP-64-laptop and a Lenovo-Ideapad-64 using both 32 and 64 versions of Debian and Ubuntu-Lucid for booting, but only Lenovo for creating CD (again, many times before without any problems).

Previous ISO's of Lucid do boot.   I recently tried creating ISO's from 32Karmic and 64Lucid, none worked except Knoppix.  I generally use wodim but to verify also used brasero.

I played and worked with computers over 40 years and know what I am doing, WHAT HAPPENED?  CD's "look good" but are not bootable.  YES, all files are displayed on CD, not xxx.iso.