This is the solution. I have a Win 7 machine at home with multiple user accounts. Yesterday, I installed Office 2010, and my account (used for the installation) worked fine, but my wife’s account had the “Outlook data file cannot be accessed” issue. Following these steps (provided again below) easily fixed the problem and Outlook immediately began sending and receiving without having to reboot, close and re-open Outlook, or any other tweaks.
Changing the folder to specify Inbox fixed the issue. Apparently the inbox did not get set and the higher level file name was selected.
1. From Outlook 2010 click File>Account Settings>Account Settings
2. adaugire by me: pentru fiecare cont de acolo
2.1. Click Change Folder
2.2. Click the + to the left of the folder name to expand the subfolders. Click orice in afara de Inbox. Click OK.
3. Close Account Settings
4. repeti pasii 1-3 cu exceptia faptului ca acum alegi Inbox
5. Close Account Settings and click send/receive.