imp logout when resizing window netscape 4.7x

[Saskia Vandamme]

I have

$this->registry['auth']['login'] = 'imp';
$this->registry['auth']['logout'] = 'imp';

When I resize my window in Netscape 4.7x I get logged out of imp, I am
still logged in to Horde.
Not in Netscape 6 or Internet Explorer.

How can I solve this problem?