When transferring a domain name or updating your Name Servers for the domain, your local computer DNS servers might be still resolving your old site IP or perform queries to your old domain's DNS servers - which will lead to either you not being able to access your new site or you will be accessing the site hosted with your previous hosting company.
Usually after certain period of time (time to live - usually 24-72 hours) your local computer will naturally start to resolve your new site address and query your new domain DNS servers.
Clearing your local computer DNS cache (DNS FLUSH) could help expedite this process and in 90% cases, you will be able to access your new site immediately.
To clear your local DNS cache on Windows XP/2000/2003:
Click Start > Run
Enter ipconfig /flushdns in the textbox.
Click OK button.
To clear your local DNS cache in Mac OS X Mountain Lion or Lion:
In Mac OS X Mountain Lion or Lion, you can use the below command to flush the DNS resolver cache:
sudo killall -HUP mDNSResponder
To clear your local DNS cache in Mac OS X 10.6:
In Mac OS X 10.6, you can use below command to flush the DNS resolver cache:
sudo dscacheutil -flushcache
bash-2.05a$ dscacheutil -flushcache
In Mac OSX versions 10.5.1 and before:
The command lookupd -flushcache performed the same task:
bash-2.05a$ lookupd -flushcache
In combination with the above - you may need to reboot your computer and/or clear your browser cache.
If the above steps still do not help - please, allow 24-72 hours for the new DNS change to take place and propagate throughout the Internet. If after this time you still can not access your new account - please open a ticket.