You can rename or delete the USERPREF.DAT file that is in your company's folder. You will lose some other personalizations too, and it will affect all users of that company. But that's probably better than waiting hours for the window to load so you can reset the defaults.

If you need detailed instructions, read KB ID 10241.

The answer given here is 8 years old - much has changed within Sage during that time.  Does anyone have a more updated answer?  I accidentally selected All instead of a particular month to view and edit sales info.  It is 36 hours later and not only is it still "searching" but now I can't even select "view and edit sales info" to see if it's IS still searching - the option has totally disappeared.

Yes, there is a better answer now. You'll have to force Sage 50 to close. When you re-open it, log into your company and go to the Options menu and choose Global. In the Options window, go to the General tab and check the box next to "Do not save last selected Date Range in List Views."

When you open the List, it should be set to show the current period.