Unfortunately the safety of your passwords can't be guaranteed. There are too many sites with inadequate security. Having a different password for each site means that if one is compromised the others are still safe - as safe as they were before.
If crypt() uses DES the weak point would be the key. If a hacker could get that they can just decrypt everything. That's one reason why hashes are preferred to encryption for passwords. Single DES is no longer considered secure because the key length is too short, so brute-forcing is a danger too. if an attacker cared to invest the effort - perhaps not for this site.