Well, the instruction I provided seems quite detailed, don't know what might go wrong. Which browser are you using?

To troubleshoot, verify:
1) That you've got existing snurl in your account and that you can modify its destination manually
2) That destination modified manually is updated and can be retrieved on your mobile
3) That you filled all the details right in 4 strings here:
var uname = 'myUname';
var apikey = 'blahblahblah';
var snipnick = 'c2dmwannabe';
var snipPasscode = '123';

If that won't help, PM me your account details (may create a fake one if too much concerned of its safety) and bookmarklet url you're recieving from bookmarklet editor after following my instructions.
Unfortunately I didn't manage to get any code executed after the request is sent to snurl, so couldn't add response analysis, which makes troubleshooting somewhat complicated.