Almost every second refresh ends in error?! (IIS)

[eluser]Unknown[/eluser]
Hi,

I installed Codeigniter on a IIS6 machine with MSSQL and iirf_rewrite.
There are only two sites, the welcome page and a simple test of MSSQL. All seems to work perfect.

But almost every 2nd time, when I do a refresh (F5) there appear notices:

Code:

Notice: Constant SELF already defined in C:\Inetpub\wwwroot\AMHS\__CI\assist.php on line 125

Notice: Constant EXT already defined in C:\Inetpub\wwwroot\AMHS\__CI\assist.php on line 128

Notice: ...

and so on. It ends with the constants in the config/contants.php

Often PHP returns

Code:

PHP has encountered an Access Violation at xxxxxx

I suspect there is a problem with any cache? Or I`m confused and I've overseen something!

Please give me some input which can solved my problems. I know about IIS Problems but this wasn´t my decision.

Thank you

[eluser]Unknown[/eluser]
Currently I found out that the application runs stable without

Code:

$config['sess_use_database']

But maybe anyone has some tips? Why?