Windows Media Center on Vista Ultimate crashes

I installed Vista Ultimate and started media center... things worked ok for
a day or so and now it crashes when I try to start it:
Description:

Stopped working

Problem signature:

Problem Event Name: APPCRASH

Application Name: ehshell.exe

Application Version: 6.0.6000.16386

Application Timestamp: 4549b55e

Fault Module Name: EhUI.dll

Fault Module Version: 6.0.6000.16386

Fault Module Timestamp: 4549bcf9

Exception Code: c000008e

Exception Offset: 0000c19c

OS Version: 6.0.6000.2.0.0.256.1

Locale ID: 1033

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