boot cdrom error

[gaspo]

hi i have this problem now..i wanna reinstall my freebsd for have a
 fresh installation of freebsd....5.3... on my ultra5 sun server...
 but when i type:
 stop A
 ok > boot cdrom
 Can't read disk label.
 Can't open disk label package
 Can't open boot device
 ....
how is possible?
 because on this hard disk was installed solaris5.7.. i replace freebsd
 5.3 some day ago with normal installation on cd boot cdrom ecc.....and
all work...perfectly..now WITH same hard disk and same CD...i can boot
 freebsd rom cd
 
 why??
 i have tried also to reburn cdrom...change CDROM ..change Operative
 sistem...like netbsd openbsd ecc... but The only sistem boot from Cd
 is sun 10..
 anybody have any idea?