You can try the following steps and see if this fixes the issue. I am mentioning below the steps to create a new e-mail profile in Outlook 2007. It works for a problem like yours:
1. Click Start, click Run, type Control in the Open box, and then click OK.
2. Depending on the version of Windows running on your computer, do one of the following:
If you are in the Category View, click User Accounts, and then click Mail.
If you are not in the Category View, double-click Mail.
Windows Vista/Windows 7:
Click User accounts, and then click Mail.
3. The Mail Setup dialog box opens.
4. Click Show Profiles.
5. Click Add to start the New Profile wizard.
6. In the Profile Name box, type Test, and then click OK to name the new e-mail profile.
7. Click to select the Manually configure server settings check box.
8. Click Next.
9. On the Choose E-mail service page, click Internet E-mail.
10. Click Next.
11. Fill in the boxes in the Internet E-mail Settings dialog box. Make sure that the Account Type setting is set to POP3.
12. Enter the information from your ISP or from your e-mail administrator in the Incoming mail server box and in the Outgoing mail server (SMTP) box.
13. Click Next, follow the prompts to finish setting up your account, and then click Finish.
14. Your new profile is created. Follow the next steps.
15. On the Mail dialog box, under the When Starting Microsoft Outlook, use this profile box, click to select the new profile that you created in step 3.
16. Click OK.
Have you tried send/receive all option? Try it once. Also check your Internet connectivity settings as sometimes it causes this issue. If it is file then check your account profile settings. Correct these if any thing is wrong. At last if there is no mistake in settings then check your email profile and the Outlook data (.pst) file. If any error occurs in PST file then this could be one of the cause of this problem. Then you just need to repair the PST file with a good utility.