Hi Vondab,
Sorry for the delay in response.
Assuming you are using Fill & Sign services in Adobe Reader, could you please check if you have an update available for Reader.
Click "Check for updates" under Help menu. You may also download updates manually from these links:
Adobe - Adobe Reader : For Macintosh
Adobe - Adobe Reader : For Windows (reboot the machine after installing the update and try again).
You may also refer to the following links which discuss the similar issue:
Fill & Sign Issues
Can't use the fill and sign tool as the document window goes blank
Thanks,
Shivam