Which version of Mantis are you using? There was some issues with cookies that were fixed in 0.18.0aX. Hence, it is recommended to use 0.18.0 release.

I don't think any of the core development team tested Mantis on PHP5 yet.

0.18.0-CVS, latest released version at the sf download page. (downloaded from sf.net yesterday).

suggest documenting known working combos / non-working combos of php and mantis, adding warning to admin/check.php

I'm preety sure that this bug has nothing to do with PHP5 - it's somehow bug in IE browser with inproper headers sent. I came to this solution long time ago and now I reminded this issue.

So this is, I think, related to no-cache headers sent to browser. I changed this in file ./core.php in line 102

header( 'Pragma: no-cache' );
header( 'Expires: Fri, 01 Jan 1999 00:00:00 GMT' );
header( 'Cache-Control: no-store, no-cache, must-revalidate' );
header( 'Cache-Control: post-check=0, pre-check=0', false );

to my tested headers:

header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Cache-Control: private");
header("Pragma: no-cache");

and it works all great. Please consider this.

This bug is really annoying and is causing to load blank white page (you can't even see the source!) in IE (I tested it in IE 6). It affects random pages - I have'nt noticed any relations beetwen this "blanks".

I use Mantis 0.19.0 version.

I have been recently testing Mantis CVS (post 0.19.1) on Apache 2 / PHP 5.0.2. There was two main issues:

1. ADODB needed an upgrade (this was the reason for the blank pages).
2. There was a problem with mysqli_escape_string(). This was not enabling the users to login.

After fixing these issues, Mantis seems to be working without problems with PHP 5 and Apache 2. So I think 0.19.2 will officially support PHP 5 / Apache 2.