Hello all. I
have had the exactly same problem.
I've created a form with Scribus 1.3.3.14.
Some text fields and form fields are included in this PDF.
Now Adobe Reader X 10.0.x was released.
The font is gambled.

I've setup the original PDF with embedded fonts.
Tried it without embedded fonts.
It works! no gambled text
PDF settings: PDF 1.5, no embedded fonts
After some weeks, Adobe Reader X 10.1.x was released
The font is gambled again

Tried several settings, found out, that only formfields are affected with this problem.
After some try and error, following worked for me:
PDF setting: PDF 1.3, no embedded fonts.
I got a bad feeling about the next updates of the Adobe Reader ..
I have no clue what they are changing every time..
Regards
Vik