Error message (yellow) "Open basedir" etc when upgrading

[olavt]

When I was upgrading, I got two "yellow lights", saying

"Open basedir restrictions appear to be in effect. If you have SESSION problems and ini_set works, you can try to enable sessions with cookies

adding: ini_set('session.use_only_cookies', 1); to top of config.php"

I asked my ISP about these messages. They say that this was for security-reasons, and that it should be no problem with any properly programmed application.

Any comments to this?