error with array_reduce

I’ve upgraded to WP 2.6 (theme K2 version RC6). In my dashboard i’m getting the error
“Warning: array_reduce() [function.array-reduce]: The first argument should be an array in /storage/mijndomein/users/032386/public/sites/www.astroblogs.nl/wp-admin/index.php on line 118”

Can someone help me with this problem? My website (www.astroblogs.nl) seems to work properly.