[imp] ERROR on login

[G G Papazoglou]

Hi. One more post for a different issue: When I login to IMP I get the
following:

Notice: unserialize() [function.unserialize]: Argument is not an string in /usr/local/apache2/htdocs/horde/imp/lib/Session.php on line 177

Warning: Cannot modify header information - headers already sent by (output started at /usr/local/apache2/htdocs/horde/imp/lib/Session.php:177) in /usr/local/apache2/htdocs/horde/imp/redirect.php on line 117

If I refresh the page continues to load normally.

Any ideas?