ActiveSync problem - won't connect, can't open from system tray

Running a fresh installation of Windows XP SP3 and Office 2003 on my
desktop, with a fresh installation of ActiveSync 4.5; my phone - HTC
HD2/Leo - is running Windows Mobile 6.5. Windows firewall is running. The
phone is sync'ing my contacts and calendar (I've set up a separate email, so
I'm not collecting mail through Outlook.

I'm having problems with ActiveSync and would be grateful for some advice.

Firstly, when I boot the computer and connect the phone, ActiveSync opens
and syncs and I can see it on my desktop. However, once I've minimised it
to the system tray, I can't get it back on-screen, either by double or right
clicking on the system tray icon. A reboot solves this, but only
temporarily. Once this has happened, the phone stops synchronising when I
plug it into the computer with the USB cable. A reboot appears to fix the
problem, but this takes me back to problem #1...

Once I've rebooted, ActiveSync behaves perfectly well, but after a time
(overnight, in the latest instance), the phone fails to sync and, if I
"close" ActiveSync, I can no longer open it from either the system tray or
the Start menu. I've tried the workaround in the MS KB to terminate
wcescomm.exe, but it doesn't reopen when I connect my phone. Trying to
close WCESMgr.exe using the Task Manager fails - it just won't close.

I've tried uninstalling & reinstalling ActiveSync and find the same problem;
can anyone suggest what I might try to resolve the issue?

Restarting wcescomm.exe manually makes all the right noises (a
higher-pitched set of bleeps than the normal USB connection noise) but it
still fails to open on my desktop and while my phone tells me that it's
trying to sync, nothing happens. I've looked at the MS troubleshooting
guide for ActiveSync 4.2 and tried the fixes suggested, but they are either
not relevant or don't work.

The ActiveSync troubleshooting window opened for the first time today, and
after the scan offered the following diagnosis: "Unable to establish a
connection between the PC and the device." The phone was plugged in at the
time.

This is getting boring. If I really have to reboot my computer every time I
want to sync my phone, it's going straight back to the shop and I'll get an
iPhone: bizarrely, an Apple device connects perfectly happily with my
Windows PC, but a Windows device doesn't want to talk to my Windows PC.