You're correct that it has to do with ActiveX controls and macros. MS
Office uses the same security control mechanism to deal with both of
them. From the symptoms, you have the macro security level (in Tools >
Macro > Security) set to high, that is, disable all unsigned macros.
That also disables ActiveX controls, which causes the document
containing them to open in design mode.

The most sensible way to handle this is to set the security level to
medium. When you open one of these documents, you'll get a warning
dialog with Disable, Enable, and Cancel buttons. If you trust the
sender, click the Enable button and the document will open without the
toolbox. If you click Disable, you'll get the toolbox; if you click
Cancel, the document won't open.

Setting the level to low is not recommended, as it allows any macros
or controls in the document to run without warning you. It's like
removing the batteries from your smoke detector because you get a few
false alarms.

--
Regards,
Jay Freedman
Microsoft Word MVP         FAQ: http://word.mvps.org