If you are using a dual monitor or changing your monitor resolution, it is possible to ‘lose’ your Formula Editor.  This is because the window tries to remember where it was last positioned, and it is possible that the last coordinates are now outside your current monitor’s visible area.  You have to set the coordinates of the Formula Editor window to be within your current view.  [update 8/2013 – I have posted another method you can try before digging into the registry as suggested below.]

If the  method in the updated post doesn’t work, you will have to go into the registry, which is something that you should do very carefully, and (to be safe) after creating a restore point for your system or backing up the registry.

For Version 12, close Crystal Reports first and then follow these steps:

• Click the Start button and select “RUN”
• Type “Regedit” and Click “OK”
• Find the Registry key:  HKEY_CURRENT_USER\Software\Business Objects\Suite 12.0\ Crystal Reports\Formula Workshop
• Change the “Editor Position” value to 10,10,10,10

Versions 9 – 11 have a slightly different registry key but they still require you to change the “Editor Position” value as shown above for version 12.

For version 11 use this registry key:
HKEY_CURRENT_USER\Software\Business Objects\Suite 11.0\ Crystal Reports\Formula Workshop

For version 10 use this registry key:
HKEY_CURRENT_USER\Software\Crystal Decisions\10.0\Crystal Reports\Formula Workshop

For version 9 use this registry key:
HKEY_CURRENT_USER\Software\Crystal Decisions\9.0\Crystal Reports\Formula Workshop

Version 8.5 is completely different. Use this registry key:
HKEY_CURRENT_USER\Software\Seagate Software\Crystal Reports\Dialogs
Look for the property called FormulaEditDialogInit.
Change the first 4 numbers of this to 10,10,10,10 and leave the rest )

This info is based in part on SAP Technical Note 1374826