About your access issue once again:
1. Make sure that your sitemap rule is before vBET ruels
2. Make sure that your sitemap rule is finishing one (has L in []), example:
Code:
RewriteRule ^((urllist|sitemap_).*\.(xml|txt)(\.gz)?)$ vbseo_sitemap/vbseo_getsitemap.php?sitemap=$1 [L,R=301]
On one of our forums which uses subdirectory in URL we modified rule adding forum directory at the beginning (because of dump redirects):
Code:
RewriteRule ^((urllist|sitemap_).*\.(xml|txt)(\.gz)?)$ /forum/vbseo_sitemap/vbseo_getsitemap.php?sitemap=$1 [L,R=301]
If you still have issue please let us know