See if this KB article applies:
Incorrect font is applied after a style is applied to a form field in Word
2007 or in Word 2003
http://support.microsoft.com/kb/828501/en-us
--
Stefan Blom
Microsoft Word MVP
"Justin" wrote in message
...
We've discovered what appears to be a glitch within Word 2007 tables when
using legacy text form fields within protected table cells.
We have defined Arial as our global font within Normal.dotm, and initially
when we create the form fields in the table cells the default font
applies.
However, after the form is protected and users input text into the form
field, if they use the delete key repeatedly to remove the text, it
somehow
is changing the properties of the form field which results in the font
changing to Cambria Math.
I've been able to recreate the problem, and it only happens with legacy
text
fields that reside in protected table cells, if you don't use the delete
key
past the last character the default font remains, on extra delete past the
last character and you can visually see the size of the text field change
and
convert to the new font.
Any ideas?