Strange error including DB.php

I have been searching for days and have been unable to come up with an answer for this strange problem. I'm trying to use the PEAR DB library with a site I'm developing. To include the library in the scripts, I'm using: require_once 'DB.php'; About 20% of the time, my scripts will execute properly. The other 80% of the time, I get this error: Fatal error: Failed opening required 'DB.php' (include_path='') in /home/dpmusic/public_html/admin/dbconn.php on line 2 My scripts do not contain anything that modifies the include_path, and I'm using a pretty reliable host (he.net). My phpinfo() output reports that my include path has been configured to .:/usr/local/lib/php. This is php 4.1.2. I emailed them about the problem but have yet to recieve a reply. I tried simulating the problem with a dummy script which does not exist anywhere on the server. The following code: require_once 'Foobar.php'; Returned the following error: Fatal error: Failed opening required 'Foobar.php' (include_path='.:/usr/local/lib/php)... Notice that in this error, the include path shows up, but it doesn't when I try to use PEAR. Any thoughts on a possible solution to this would be greatly appreciated. Tom