Answered Please help: working site suddenly doesn't work

My MODX site has been up and working for nearly a year. I haven't changed anything recently. The site was working earlier today, but all of a sudden, it's offline. Http is up and working, but I'm getting 500 Server Error when I go to the home page. I've restarted Apache and I've restarted the server.

Just before it went completely down, I was in manager, and it showed Website in the Resources tab, but it didn't show anything under it.

Server is RHEL 6, version is 2.2.1, I believe.

Any suggestions about where to look or what to do would be hugely appreciated. Honestly, I don't even know where else to start looking.

Bob, you are absolutely amazing. That was it--core/cache. I deleted everything and suddenly, the site is back and manager is working again.

You have totally saved our site, at a really critical time. I wish I could do something commensurate for you, but please know that we're really grateful to you for the help. (And if I ever can help, it would be a true pleasure!)

I'm glad I could help.

You should definitely upgrade MODX (try the UpgradeMODX extra). The 2.2 versions suffered from cache corruption and have serious security issues as well. I'd advise upgrading to 2.3.0, then 2.3.6, then 2.4.2 rather than doing it in one jump.

BTW: http://bobsguides.com/support-this-site.html