looks like your php running as nobody. to confirm this:
#ps -ef|grep php
and please post /home/userhost/public_html/.htaccess here.
==================================
root@server14 [/home/userhost/public_html]# ps -ef|grep php
parsinfo 3197 25277 11 13:57 ? 00:00:09 lsphp5
kocholo 3199 25278 7 13:57 ? 00:00:06 lsphp5
shiadost 3203 25278 2 13:57 ? 00:00:01 lsphp5
shiahaco 3214 25278 8 13:57 ? 00:00:04 lsphp5
kocholo 3228 25278 8 13:57 ? 00:00:03 lsphp5:/home/kocholo/public_html/modules.php
parsinfo 3241 25277 5 13:57 ? 00:00:01 lsphp5
shiahaco 3447 25278 10 13:58 ? 00:00:02 lsphp5:/home/shiahaco/public_html/index.php
filmsaz7 3451 25278 1 13:58 ? 00:00:00 lsphp5
dehkadey 3452 25278 7 13:58 ? 00:00:01 lsphp5
buxbazco 3453 25278 0 13:58 ? 00:00:00 lsphp5
urpatogh 3456 25278 6 13:58 ? 00:00:01 lsphp5
urpatogh 3457 25278 1 13:58 ? 00:00:00 lsphp5
urpatogh 3460 25278 7 13:58 ? 00:00:01 lsphp5
acrofull 3461 25278 3 13:58 ? 00:00:00 lsphp5
modir 3474 25278 2 13:58 ? 00:00:00 lsphp5
birdesig 3490 25278 4 13:58 ? 00:00:00 lsphp5
nanopark 3492 25278 0 13:58 ? 00:00:00 lsphp5
root 3506 26811 0 13:58 pts/1 00:00:00 grep php
modir 27212 25278 0 13:24 ? 00:00:04 lsphp5:/home/modir/public_html/live/server.php
==================================
root@server14 [/home/userhost/public_html]# cat .htaccess
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
Options +SymLinksIfOwnerMatch
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress
RewriteCond %{HTTP_HOST} ^sampledomain.com$ [OR]
RewriteCond %{HTTP_HOST} ^www.sampledomain.com$
RewriteRule ^/?$ "http\:\/\/www\.sample\.com" [R=301,L]
==================================