Several changes were made to the "sd" driver between 2.3 and 2.4.
In particular, the code that resets the drive to the 512 block size
is no longer called in the case of a data overrun. Accordingly, it
is not currently possible to install 2.4 from a local non-Sun
CDROM drive. Your best bet for the short term may be to either
borrow a SunCD (locally or maybe from your Sun Rep) or to mount the
CD remotely on a machine that is already up and running and can
handle your non-Sun CDROM, and perform a network installation.
This is not a problem for non-SPARC versions of Solaris 2.x.
CDROMs that have been modified to use a 512 byte blocksize by default
will work fine.
The Sun CD-ROM FAQ explains how to patch Solaris 2.x for using a
non-Sun CD-ROM drive for booting/installation. It also includes
other information about using CD-ROM drives on Sun.