Two thoughts. First, go to tools, accounts, highlight your other acccount, and then click on set as default. This will make the other account your primary on replies, and for receiving e-mail
On the account that is not receiving but can send, it must be an incorrect server setup. Click on tools, accounts, then highlight the non-working account. Click on properties, then on the servers tab. Make sure if your account is a POP3 that that is selected as the incoming server. Then check that the incoming mail server is correct per your provider. Finally, make sure that the account name is correct. Most times it is your user name, but Earthlink, for example, requires the entire (e-mail address removed)
Make sure that on the general tab, include this account when receiving mail is checked
Hope this helps