FIRST DEBUG SESSION:
in the install process:

file to edit:
install/hacks/GRPS/x/queries.php

$query['new'][] = 'ALTER TABLE ' . TABLE_PREFIX . 'usergroup ADD arcadepermissions INT(10) UNSIGNED DEFAULT 0 NOT NULL';

is useless, and try to override some ARCADE permission..
EDIT: not useless, just error:
$query['new'][] = 'ALTER TABLE ' . TABLE_PREFIX . 'usergroup ADD grpspermissions INT(10) UNSIGNED DEFAULT 0 NOT NULL';


also, change the " ` " for " \' " .. or the queries does not finish in some mysql servers.
.. and these queries at the end ... $query['new'][] = 'INSERT INTO grps_categories
are missing their ending " ) " ...

OTHER EDIT:

??In your /forums/includes/functions_bbcodeparse.php file:

.. there is two occurences of what you need to replace... this is not stated in the process...

??In your /forums/clientscript/vbulletin_editor.js.php file:

this thing to modify:

window.open("../forums/misc.php

you need to edit it more properly and indicate the proper url to your forum, the ../forum is not the same for everyone!

??In your /forums/admincp/adminfunctions_template.php file:

'groups' => 'GRPS', <<< add the " ' " please... to be PHP perfect!

??In your /forums/includes/functions.php file:

\/\/ declares the arcade image directory <<< ARCADE ghost ?!
these \/\/ are not legal comments... use // always !!!



??In your navbar template:

search have to be modified for a default install (missing the accesskey thing!):
<span class="navbar"><a href="$vboptions[forumhome].php?$session[sessionurl]" accesskey="1">$vboptions[bbtitle]</a></span>

and replaced by this:
<span class="navbar"><a href="$vboptions[forumhome].php?$session[sessionurl]" accesskey="1">$vboptions[hometitle]<if condition="THIS_AREA == groups"> Groups<else /> $vboptions[bbtitle]</if></a></span>

(btw, will need a $vbphrase for the title!)