Hello, this problem same for me.
.htaccess file is wrong
If you edit a post or make a post .htacces fail
I believe that following lines are wrong:
#Rewrite Old urls
RewriteRule ^index.php/board,(.*).html seo4smf-redirect.php?b=$1 [R=301,L]
RewriteRule ^index.php/board,(.*).html;(.*) seo4smf-redirect.php?b=$1&o=$2 [R=301,L]
RewriteRule ^index.php/topic,(.*).html seo4smf-redirect.php?t=$1 [R=301,L] # WRONG (no edit, no delete, no make post)
RewriteRule ^index.php/topic,(.*).html;(.*) seo4smf-redirect.php?t=$1&o=$2 [R=301,L](no edit, no delete, no make post)
The regex are wrong in this url (some examples):
index.php/topic,674.msg6885.html#msg6885 ==> seo4smf-redirect.php?t=674#msg6870 (FAIL==> Error 500)
How it solve?
What the regular expression is right?
PD: Sorry for my bad English