I love the new walk-through installation in BuddyPress, unfortunately i was unable to get BuddyPress installed and working correctly on my local XAMPP setup. It is a very advanced XAMPP setup so BuddyPress probably cannot handle interpreting my vhosts file correctly or maybe it is something else, but after spending an hour just trying to get BuddyPress to work i had to throw in the towel.
I notice that on installation BP wipes out the existing .htaccess code and writes new .htaccess code, which is fine and is probably done with wp rewrite flush function. No big deal here.
Ok since i cannot see this visually quickly and digging through the BuddyPress coding would take too much time that i cannot spare right now so here is an alternative solution.
Do not apply BPS security to BuddyPress Forum. This is obviously not an optimum solution, but at this time I cannot fiddle around with this. Next week i will have some time to spare to find out exactly what the issue is.
An example of the bypass / skip rule that you would use to not apply security to the BuddyPress Forum area would be something like this and it would go above skip rule #12
# BuddyPress Forum bypass / skip rule
RewriteCond %{REQUEST_URI} ^forum/ [NC]
RewriteRule . - [S=13]
Or i just thought of something else. If you can get the error from one of your log files - either Server log or php error log then it will probably contain the query string in the logged error. Once i know what the query string is then i can quickly create the bypass / skip rule for that query string.
