I've enabled

Search Engine Friendly URLs
Use Apache mod_rewrite
Add suffix to URLs

And changed my .htaccess, to this:

##

# @version $Id: htaccess.txt 14401 2010-01-26 14:10:00Z louis $

# @package Joomla

# @copyright Copyright (C) 2005 - 2010 Open Source Matters. All rights reserved.

# @license http://www.gnu.org/copyleft/gpl.html GNU/GPL

# Joomla! is Free Software

##





#####################################################

#  READ THIS COMPLETELY IF YOU CHOOSE TO USE THIS FILE

#

# The line just below this section: 'Options +FollowSymLinks' may cause problems

# with some server configurations.  It is required for use of mod_rewrite, but may already

# be set by your server administrator in a way that dissallows changing it in

# your .htaccess file.  If using it causes your server to error out, comment it out (add # to

# beginning of line), reload your site in your browser and test your sef url's.  If they work,

# it has been set by your server administrator and you do not need it set here.

#

#####################################################



##  Can be commented out if causes errors, see notes above.

Options +FollowSymLinks



#

#  mod_rewrite in use



RewriteEngine On



########## Begin - Rewrite rules to block out some common exploits

## If you experience problems on your site block out the operations listed below

## This attempts to block the most common type of exploit `attempts` to Joomla!

#

## Deny access to extension xml files (uncomment out to activate)

#<Files ~ ".xml$">

#Order allow,deny

#Deny from all

#Satisfy all

#</Files>

## End of deny access to extension xml files

RewriteCond %{QUERY_STRING} mosConfig_[a-zA-Z_]{1,21}(=|%3D) [OR]

# Block out any script trying to base64_encode crap to send via URL

RewriteCond %{QUERY_STRING} base64_encode.*(.*) [OR]

# Block out any script that includes a <script> tag in URL

RewriteCond %{QUERY_STRING} (<|%3C).*script.*(>|%3E) [NC,OR]

# Block out any script trying to set a PHP GLOBALS variable via URL

RewriteCond %{QUERY_STRING} GLOBALS(=|[|%[0-9A-Z]{0,2}) [OR]

# Block out any script trying to modify a _REQUEST variable via URL

RewriteCond %{QUERY_STRING} _REQUEST(=|[|%[0-9A-Z]{0,2})

# Send all blocked request to homepage with 403 Forbidden error!

RewriteRule ^(.*)$ index.php [F,L]

#

########## End - Rewrite rules to block out some common exploits



#  Uncomment following line if your webserver's URL

#  is not directly related to physical file paths.

#  Update Your Joomla! Directory (just / for root)



# RewriteBase /





########## Begin - Joomla! core SEF Section

#

RewriteCond %{REQUEST_FILENAME} !-f

RewriteCond %{REQUEST_FILENAME} !-d

RewriteCond %{REQUEST_URI} !^/index.php

RewriteCond %{REQUEST_URI} (/|.php|.html|.htm|.feed|.pdf|.raw|/[^.]*)$  [NC]

RewriteRule (.*) index.php

RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization},L]

#

########## End - Joomla! core SEF Section

And i get this error:

Parse error: syntax error, unexpected T_STRING, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or '}' in /nfs/c07/h02/mnt/100144/domains/cru.st/html/components/com_communityanswers/helpers/nestedtree.php on line 20