A substantial portion of PowerCLI 4.0 U1 users report extremely slow startup. On affected systems PowerCLI takes very long (sometimes up to 5 minutes) to start. Standard PowerShell window opens as usual.
The problem appears when a machine does not have Internet access. The cause is a security feature of Windows – checking for revocation of software publisher's certificate. The problem is not specific to PowerCLI. Other applications on the same machine which use certificates are affected as well.
To avoid the delay, disable the following option:
Windows > Control Panel > Internet Options > Advanced > Security > Check for publisher's certificate revocation
For details, the original discussion in the forums is: