This has been a question that i have been pondering for quite some time. Infact i have faced this problem quite often. Luckily I have found out some solutions which work. I request readers to try out these and let me know your comments.
1. Use a different web address/URL
You can also try the following URL’s
http://www.gmail.com or https://www.gmail.com
http://gmail.com or https://gmail.com
http://m.gmail.com or https://m.gmail.com
http://googlemail.com or https://googlemail.com
http://mail.google.com/mail/x/ or https://mail.google.com/mail/x/
2. Configure your email Client to access Gmail A/C (POP Access)
If the above method didn’t work you can try configuring your mail client’s such as Outlook to access Gmail. Google has provided information on how to configure your mail client and the supported POP client list at http://mail.google.com/support/bin/answer.py?answer=12103.
3. Use Google Desktop
Download and install Google Desktop on your PC which bypasses proxies and enables you to access Gmail. This application requires Windows Vista/XP/2000 with SP3+ and has a version for Linux and Mac as well.
4. Use Gmail-lite
PS : These URL’s are not of Google Gmail but are 3rd party services.
Using these URL’s you can login to multiple gmail accounts at the same time.