WordPress MU

Is anyone using WP Total Cache and have had errors showing up int he logs over the past few days?

We love WP Total Cache and it has helped our server load immensely...but as of about 2 days ago, it is asking real funny.

We has to turn off page caching, which is a huge drain back on resources because of this error:

[Wed Dec 02 00:21:04 2009] [error] [client xxx.xxx.38.97] PHP Fatal error:  Call to undefined function is_404() in /var/www/vhosts/domain.com/httpdocs/wp-content/plugins/w3-total-cache/lib/W3/PgCache.php on line 182

It is trying to assign the variable $is_404 the value from the function is_404(). I tried to check it - and when I did, it just moved on to a is_single() function call.

It's like it has lost scope to the WP functions?

Does this problem persist with the latest version?

We're not getting the errors anymore.

We also had trouble with the database caching - it would cause errors, have you seen this before?

Can you be more specific?