Thanks for the help, t-p and webjunk,

tp:

I tried removing/naming .htaccess. No help. I still get a 404 not found error, but this time from Bluehost. When the original .htaccess was there, the 404 error was a page in the site, with the theme intact. When I remove the .htaccess, I just get a vanilla 404 error.

I can't switch themes, since I can't login to the admin area. I don't even get a login screen. I just get 404 not found (even though I can get to the site itself). http://www.erinhydequilts.com/

I do have ftp access, as I mentioned in the original post (that's how I changed .htaccess), but how do I change the theme there? Is that what you were suggesting?

webjunk:

I checked the siteurl in phpMyAdmin and it hasn't changed. It correctly targets the subdirectory where I installed Wordpress, which is what it was when it was working, as well.

When you say to check the Admin accounts, can you be more specific? The account with the name Admin is gone (I followed Sitepoints security recommendations and removed it after creating new adminstrative accounts with different names.) The three admin accounts are all showing up in the database, but I don't know what else to look for.

Thanks again. I'm in real trouble here, so I'm really grateful for anyone's help.
Cyd