1. Is the vCenter server web services started..??
2. When you installed the vSphere web client was it in a different location than c:\ or default.?
if so then
- Uninstall the vSphere Web Client.
- Reinstall the vSphere Web Client.
- During the installation, accept the default installation directory on the C:\ drive when prompted by the installation wizard.
if still problem s check the KB article http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2012473
