Replies not pre-filling the "To" field... sometimes

[markinct]

I have come across some strange behavior. Depending on which PC I use, OTRS may or may not pre-fill the "To" field when I open an 'empty answer' template. However while demonstrating OTRS to another employee opening the same template DID result in the "To" field being prefilled.

I used the latest release of FireFox on both PCs. I believe both PCs are configured the same, however this experience leads me to believe that's not the case. What setting or security measure could prevent OTRS from prefilling the TO field?