BuddyPress.org

OK, I am a total newb at this switch-over from WP standalone to BP, but I sure hope this community can help me.

1and1.com is my hosting
I successfully loaded WP 3.0
I have successfully activated the multisite capability (I see the superadmin panel, and all options are available)
I used FTP to place the extracted BP plugin 1.2.5.2 into my wp-content/plugins folder
When I log into my WP site as admin, and go to plugins, I see BP there and have the choice to click “network activate”
BEFORE clicking that I ensured that .htaccess has the mod_rewrite enabled [see my pasted in .htaccess file below]
I then logged out and logged back in to admin, and went to activate the plugin, but immediately get the following error message:
“Error 500 – Internal server error”

PLEASE HELP THE NEWB! Thanks! Jerry

P.S. is it any clue that a “buddypress.tmp” file with filesize zero appears in my /wp-contents/plugins folder?

.htaccess file contents
# .htaccess file as suggested by wordpress for multisite & buddypress
# BEGIN BELOW

RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ – [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ – [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*.php)$ $2 [L]
RewriteRule . index.php [L]