"The local farm is not accessible. Cmdlets with FeatureDependencyId are not registered."
At first I ignored this message, but when I tried to do some configuration using the Get-SPEnterpriseSearchExtendedQueryProperty cmdlet I got the following error, indicating the this cmdlet wasn't registered:
Apparently, this cmdlet is one that runs on farm level.
01/05/2010 08:58:28.03 PowerShell.exe (0x2618) 0x10F4 SharePoint Foundation Database 3351 Critical SQL database login for 'SharePoint_Config_SP2010DEMO' on instance 'sql' failed. Additional error information from SQL Server is included below. Login failed for user 'DEMO\mark'.
When I made sure my account had sufficient rights, the problem was solved!
I guess this problem can pop-up in other occasions as well, so my advice is to check the log as soon as you encounter similar problems!