Warnings on blog page (expects parameter 2 to be string, array given)

Hello,

I’m seeing these warnings in a blog page and single posts (not in “static” pages):

Warning: explode() expects parameter 2 to be string, array given in /home/xxx/public_html/xxx/wp-content/plugins/seo-ultimate/includes/jlfunctions/arr.php on line 50

Warning: array_map() [function.array-map]: Argument #2 should be an array in /home/xxx/public_html/xxx/wp-content/plugins/seo-ultimate/includes/jlfunctions/arr.php on line 51

Warning: array_map() [function.array-map]: Argument #2 should be an array in /home/xxx/public_html/xxx/wp-content/plugins/seo-ultimate/modules/meta/meta-keywords.php on line 125

Warning: array_diff() [function.array-diff]: Argument #2 is not an array in /home/xxx/public_html/xxx/wp-content/plugins/seo-ultimate/modules/meta/meta-keywords.php on line 127

Warning: array_slice() expects parameter 1 to be array, null given in /home/xxx/public_html/xxx/wp-content/plugins/seo-ultimate/modules/meta/meta-keywords.php on line 128

Warning: implode() [function.implode]: Invalid arguments passed in /home/xxx/public_html/xxx/wp-content/plugins/seo-ultimate/modules/meta/meta-keywords.php on line 129

I can’t provide the URL because it’s under construction.
I’m using the Currents theme (by Woo Themes), with Polylang to manage 3 languages.

Can you please tell me how to fix these warnings? Thank you.

https://www.ads-software.com/plugins/seo-ultimate/