Solaris 2.4 and later (and Solaris 2.3 w/ high rev kernel jumbo patches) limit the number of ICMP error message to one per 500 milliseconds. To switch off this feature, use:
/usr/sbin/ndd -set /dev/ip ip_icmp_err_interval 0
In Solaris 8 the rate limiting mechanism was changed and traceroute will get all responses now as the new mechanism accepts short burst even though the rate limit is still in effect.