Hi,
One of my customers recently was having this issue with Screen agent version 8.X and to resolve I had to upgrade all the screen agents to SP9. Might be a good idea to check this out. If you are going to upgrade the screen agents to SP9 you need to firstly remove the previous version, restart and install the new one. Trying to run the install over the top of the installed version will not work (I found out the hard way!!)