Search throws white page of death

Whenever I try to search from my site, I get the white page of death. I’m really confused because at some point it did work- but now it doesn’t. Here’s what I’ve done so far:

1. Deactivated all plugins, checked site, then re-activated one at a time
2. Checked using default twenty-eleven theme
3. Checked using the twenty-ten theme

Now strangely, when using the twenty-ten theme, I can actually do a search. (It doesn’t find anything because I have custom post types, but at least it’s not the white page of death.)

ANY help at all is appreciated, the site’s supposed to launch in a few days– it went unnoticed because at some point, it was working.

Here is a list of files that may help:

• Functions– the changes I made so that custom post types could be searched and viewed in categories/archives.
• Searchform php
• Search php

*Update: I downloaded a fresh copy of the twenty-eleven theme and twenty-ten theme. And it works on both (no results as before, but thats ok)- so there’s something wrong with my theme; I just don’t know where to look to figure out the issue