When you say "blank box", do you mean that the tool is blank? Here's a post from the ArcGIS forums with some things to try. Text is reproduced below:
You may want to try resetting your Esri application data and registry keys. Please follow these steps to do so:
Please note: Renaming the Application data will result in loss of folder connections, SDE connections, and toolbar locations since it rebuilds the template back to the out of the box feel. Also, editing registry entries can cause issues on your computer. Please be careful when making these changes.
A) Rename ESRI Application Data folder.
- Close all ArcCatalog, ArcMap applications.
- Browse to the following directory: C:\Documents and Settings\<user profile>\Application Data (you may have to turn on hidden files).
In Windows 7/Vista:
C:\Users\Username\Applications Data\Roaming(you may have to turn on hidden files from the control panel, go to Appearance and Personalization/Folder Options/Show hidden files and folders)
- Rename ESRI folder to ESRI_OLD.
B) Rename the ESRI folder in Registry.
- Start Menu, Run, type "regedit"
- Expand HKEY_CURRENT_USER folder
- Expand Software folder within HKEY_CURRENT_USER
- Rename the ESRI folder to ESRI_OLD
The other good thing to check is if someone else in your company can log onto your machine with their username and password and reproduce the problem. If they also have blank tools, there is probably some kind of conflict preventing the tools from working properly. If they can use the tools, then your windows user profile has become corrupt to the install of ArcGIS and a new profile is needed for functionality to return.
(Thanks to Stephanie W. at Esri)
If these steps do not work, you might want to search ArcGIS forums using terms like blank or empty tool.