This seems to be more of a Linux kernel problem than an installer problem,
The installer is unable to correctly locate RPMs on the CDROM after the
"installing image to hd" and "preparing to install" stages of the
installer, presumably because the drive spins down during that long amount
of inactivity, returning errors on terminal 4 after the installer finally
tries to access it again.
I have been able to get around the problem by switching to terminal 2
during the above mentioned stages and doing an 'ls' (or other access to the
disc) in the CDROM's directories every few minutes.
I also had this problem with 6.2. I can replicate the error after
installing by mounting a CD, changing to one of its directories, waiting,
and then trying to tab-complete a filename. The error reported is the same
as that reported on terminal 4.
The CDROM model is correctly identified by the BIOS and Linux as:
hdc: ZIPCD 4x650, ATAPI CDROM drive
*** This bug has been marked as a duplicate of 15982 ***
I'm not sure that this should be marked as duplicate of 15982. Although the fix
may be related to the fix for that problem, the discs I used *are* valid images,
verified with MD5SUMs, and I was able to install using the method outlined above
(keeping the CD spinning in the drive instead of allowing it to spin down) from
them without flaw.