Top menu styling is lost when upgrading Joomla

fresh install this morning

no update applied yet

dir.renewablesandenvironment.com/
Fatal error: Call to undefined function mb_internal_encoding() in /home/renewabl/public_html/dir/components/com_k2/helpers/route.php on line 61

See this:

themerepublic.com/forums/question/fresh-...etting-k2-error.html

it should be some server component

thank you for that

before pic shows after component installed

after showing after update to 3.1.1 and on right nav menu class

I don't quite understand your question , you you better explain?

the question is how do i get the menu to work

original install was fine but when i update joomla to 3.1.1 it breaks the menu like in pic 2

the menu class suffix is nav which was a problem with the person at the start of this post

i looked at firebug and the code is <ul class = nav menunav>

Ok, I will need link for that.

EDIT:

Menu Tag ID = nav , on picture it look like you set suffix instead?