1.5.4 upgrade to 1.6 - router errror

[eluser]Tobz[/eluser]
Hi,
Im just trying to upgrade to CI 1.6 and get these errors:

A PHP Error was encountered
Severity: Notice
Message: Undefined offset: 0
Filename: libraries/Router.php
Line Number: 187


A PHP Error was encountered
Severity: Notice
Message: Undefined offset: 0
Filename: libraries/Router.php
Line Number: 193


A PHP Error was encountered
Severity: Notice
Message: Undefined offset: 0
Filename: libraries/Router.php
Line Number: 196


I have followed the upgrade instructions.
I am using custom locations for system and app folders - full system paths for both.

anyone else have this problem??

Chur,
Tobz


update: this only happens when at root of the site. other pages work fine.
also works if I put index.php in url bar

I should note that Im using htaccess to get rid of index.php from the url string