I've been having the exact same problem - not just with our exchange 2007 but one of 2003 networks is having some issues.
I was going to log it with support, maybe we both should.
I have the issue on my own laptop - so I disabled email scanning for good on all my installs till this get figured out. I'll have to rely on the exchange scanners.
Is your LDMS 8.7? Are you already on 8.7 SP5? There are several patches since 8.7 SP1.
I'm using 8.8 - so the problem has been around for a while. My outlook and exchange are also fully patched.
we're running version 8.7.0. IHMO there are only notebooks having the problem. or has anyone a desktop system having this issue?
For those of you that are running LDMS 8.7, make sure that you have the latest Antivirus updates. If you look at the properties of your Antivirus icon on your system tray it should show the engine version. If you have a build that is .7x, you need to upgrade to the latest build which I believe is .81. This is included in Service Pack 5 for LDMS 8.7.
It includes many fixes, performance enhancements, etc.