500 error after upgrading to 2.0.5 — Nothing fixes it

Hokay. I downloaded Mark’s .zip file of files that are upgraded between 2.0.4 and 2.0.5 and uploaded them to my server. Checked all permissions (everything at 776). Got the 500 error but apparently that’s common, so I tried to get the plugin Mark posted to fix it. Can’t access my plugins page, either by logging in or going directly to plugins.php — it’s all 500 “Internal Server Error”s. So I went one step farther and made the change by hand as Mark suggests to another stuck user. STILL no change. The website itself (www.puredoxyk.com) comes up with no themes or anything (but I just re-checked the themes folder and all the permissions seem correct). Any help at this point would be fantastic!