I manage two websites, with a very similar structure. One is my blog the other is a large film magazine site, but the structure is almost identical.
I was getting "Error establishing a database connection" and after trying numerous things, I've found in phpMyAdmin that the table 'truewp_options' only had 2 entries. Other tables seemed fine, with no odd looking entries (although some have thousands so who knows).
If I import the equivalent table from my blog's database and edit the entries that I need to (siteurl, home etc - *also* what would these be) would that work in recovering access?
Our last backup of the posts xml was of after publication of 300 articles, and we just covered a big festival. Can't remember when last database backup was (I have one, but after the error occurred).