As long as the mouse is used the connection remains open, but as soon as a key on the keyboard is pressed the connection to Accowin Online is lost. This is a known problem with Microsoft's RDP client on a Mac computer with a PowerPC processor. As long as Microsoft does not fix this bug the only solution is to install the old RDP client from Microsoft. 

This can be downloaded from here

More explanation about the installation and system requirements can be found here (at the bottom right of the page)