I get a 500 Internal Server Error on and off when I try to visit my site or login. Some days, it's no problem, other days, it's completely down. Sometimes I can see the site but I can't login. Sometimes I can login but I can't see the site.

Error log says: PHP Warning: Invalid argument supplied for foreach() in /hermes/web01c/b1289/moo.emrivermodelcom/wp-content/themes/atahualpa/functions/bfa_ata_admin.php on line 459

I'm running the most recent versions of WP and Atahualpa (with all bug fixes, too). I've disabled all plugins (didn't help). Htaccess file doesn't seem to be corrupted, either.

I don't know php. Do I just need to find someone who does? Or is there some fix for this that I can do myself?

So, you are running atahualpa 3.6.7?
Do you use any page templates?

Yes, running 3.6.7.

And we are not using any page templates.

Who's the host?
How much memory does php have?

FatCow is our host.
According to the htaccess file, php memory is limited to 100 MB.

are there any other messages? line 459 in bfa_ata_admin.php is

</td>

can you look at your bfa_ata_admin.php and tell me what you have at line 459
Since this is a sporadic issue, my gut says it is a server memory issue and just because the htaccess file says 100M that doesn't mean the host actually allows you to have that much memory.

I just did a google search using 'fatcow php memory limit' and found this tidbit from http://www.fatcow.com/knowledgebase/...ArticleID=1290

Memory: Some PHP CMS applications may need a larger memory_limit than the default set in the php.ini. You may change this limit in your php.ini, however, do not exceed the maximum of 64M.

you may want to change your htaccess

Line 459 says </td>, but there's a forreach statement on 462...so maybe that's where it's messing up.
There are no other messages in the error log.

Turns out, my htaccess file actually hasn't been turned on at all this entire time (b/c it didn't have the "." in front of it). I just tried turning it on (but putting the "." in front of the htaccess file), and it made things worse (still a 500 error, but with a different explanation). So it's off again (and site is running - for now).

what are the other messages?

You mean with the newer 500 error? It's just more detailed. Like, instead of it saying: "The server encountered an unexpected condition which prevented it from fulfilling the request (which is the error message we've been getting)," it says pretty much the same thing, but then it suggests I contact my administrator at webmaster@mysite.com. It's really not much different, but it's a little different from the one we usually get. I think it just means it's a different problem. Obviously the most recent one is due to the htaccess file...and the one we usually get is due to this mystery problem we are trying to diagnose.

Sorry if that wasn't the answer you were looking for. If you were talking about the error logs, there hasn't been any change. Just another PHP Warning...error on line 459. Even when the 500 error looked different and it was due to something else, error logs still said the same thing.