Warning: array_merge() [function.array-merge]: Argument #1 is not an array

Hello,
I got a problem. Whenever i push the “Place Order” button, it does not go to the next page, and gives me the following error:

Warning: array_merge() [function.array-merge]: Argument #1 is not an array in /home/deb61531/domains/drive2b.nl/public_html/wp-includes/post.php on line 2996
{“result”:”success”,”redirect”:”http:\/\/www.drive2b.nl\/login\/winkel\/afrekenen\/betaal\/”}

Is there a way for this to be fixed?
Thanks in advance.

With kind regards,
Bram van der Sanden

http://ww.wp.xz.cn/extend/plugins/woocommerce/