My b2evolution Version: Not Entered

hello
i hope this will be my last problem.
after creating subdomain i can not log in from subdomain. if login from main login form the session expires while changing the blog.

#my domain is- myseda.com

# b2e is installed under- public_html/voice

#subdomain folder- public_html/voice/med (this where my first blog as subdomain is placed) and url is med.myseda.com

#next blog folder root- public_html/voice/med/std and url is med.myseda.com/std

i tried everything using forum but still not working
is it a baseurl problem or cookie or both ( the baseurl is set to "myseda.com/voice/"
plz help me out