If you're an Arvixe user, we now advise adding this to your .htaccess file in your domain's webroot:
Header set Set-Cookie "VC-NoCache=1; max-age=900; path=/"
Header set VC-NoCache "1"
If you don't have a public_html/.htaccess file then create a blank one just containing this code.
This change may be necessary due to a caching change made recently on Arvixe's infrastructure. Aggressive caching is stripping cookies from server-side cached web requests.