I'm having a very strange issue, where PHP include and require statements fails after a number of executions.
The site is running on IIS 7/Windows 2008 R2 and the site's content is stored in a remote share on another Windows Server 2008 R2.
PHP is version 5.3. The same thing does not happen when using version 5.2.
A test page with a require statement would work fine and after a number of refreshes it would start failing with the following error (in this case a warning, if it where a require statement it would throw a fatal error).
Warning: require(./site-header.php): failed to open stream: No such file or directory in \mynas\myshare\mysite\index.php on line 17 Fatal error: require(): Failed opening required './wp-blog-header.php' (include_path='.;C:\php\includes') in \mynas\myshare\mysite\index.php
Recycling the application poool would clear the condition for a little while until it happens again.
It is worth noticing that the issue does not show at all if the include is absolute.
Would appreciate any hints in how to troubleshot this issue.