This error happens when your PHP scripts are generating errors when trying to decode multiple (hidden) eval calls in a loop.
Generally happens when the site is compromised by a script injection (or backdoor) that is causing the site to fail.
<b>Warning</b>: include(/home/xxx/test/old/wp-admin/test/cache.php) [function.include]: failed to open stream: No such file or directory in <b>/home/xxx/.bash(10) : eval()'d code(3) : eval()'d code(3) : eval()'d code(3) : eval()"d code on line <b>1</b>
It needs to be verified what is causing the error (hacked or hosting error). Sign up with us to get it fixed: http://sucuri.net/signup