I have Google Apps account and was login into it using mail.google.com/a/my_domain_name and I was using my person Gmail by going to mail.google.com.
Now, I got some email from Google, and when I go to mail.google.com it actually takes me to my Google Apps account instead to my personal account (@gmail.com).
Does anybody know how to solve this?
I have the same issue and I resolve it by having a private window within Chrome and a normal chrome browsing window with each account open in the respective browser window. It stinks because notifications from my desktop client will still try an open the default browser, but it is a decent work around.
Google keeps track over you last logged in account (if you do not log out) and that is why you are being redirected to your Google Apps account when you log into Gmail.
The two solutions that come to mind (there might be others) on how to solve this would be:
You can log in to a Personal account and an Apps account simultaneously. Click on your account name (next to the tools icon top right) when logged in on one account, select "Switch account" and then "Sign in to another account", enter your second account details. Now you can switch in one window between the Apps account and Personal one by selecting "Switch account" again and then choosing which one to view. That's how I get around having an Apps and Personal account anyway.
The other problem here could be if, when you came on to Google Apps, you already had a matching personal account for that email address. e.g. Personal account with email of fred@fred.com and then you set up fred.com on Google Apps. Then, all your Personal accounts would have been moved to username+personal@fred.com, e.g. fred+personal@fred.com to prevent any clashes... So you might need to use the +personal email address to log in to that account.
It sounds like you have multiple sign-in enabled. You can go to https://www.google.com/accounts/ to turn it off.
Google also offers a list of options for handling multiple accounts here
