Using GW 8 with client 8.0.2.

It happen only on one of the stations.
When I try to answer an e-mail or create a new mail I can't enter\type any text in any of the fields .

I solved it by changing Tools > Options > Environment > HTML browser from Default Browser to Microsoft Internet Explorer.

Any Idea why it happen?
Why on other stations it works with the "Default Browser" option?
How can I fix it?