installation/directory problems

i host with 1and1 and my sites were working fine until i updated. now i get a ‘Error establishing a database connection’ message when trying to go to my site. i’ve check my passwords/info 10+ times, i know its correct. this is the first time i’ve ran 2 sites from one 1and1 package, so its the first time i’ve dealt with directories or perhaps subdomains. whats the deal? where am i going wrong?
Z