Having just rebooted my laptop, I clicked on the link to open VMWare Infrastructure Web Access in the my browser and was slightly puzzled by the "page cannot be displayed" error. I figured it was probably the VMWare Server Web Access service not starting for some reason, so I opened services.msc and checked it out. The Web Access service was actually running, but the Host Agent service was not, so I tried to start it – it failed. Dutifully opening Event Viewer for some more information I found the error:
The VMware Host Agent service terminated with service-specific error 4294967295 (0xFFFFFFFF).
Great. Thanks for the elaboration. Time to check the VMWare logs, (c:\ProgramData\VMWare\VMWare Server\) – the most recent of which contained the following entry:
[2009-02-18 10:55:27.908 'App' 4408 info] Trying hostsvc
[2009-02-18 10:55:27.948 'App' 4408 panic] error: not well-formed (invalid token)
[2009-02-18 10:55:27.948 'App' 4408 panic] backtrace:(backtraces not supported)
[2009-02-18 10:55:27.948 'App' 4408 info] Win32 service stopped
A bit of Googling pointed me in the right direction, "not well-formed" refers to the XML config files which are stored in c:\ProgramData\VMWare\VMWare Server\hostd, after that it was just a case of opening each one in turn until I found the malformed one. I backed it up and replaced it with a default version, and lo and behold, my services started!