Powershell: deinstall

$app = Get-WmiObject
-Query "SELECT * FROM Win32_Product WHERE Name = 'Software Name'"

$app = Get-WmiObject -Class Win32_Product `
-Filter "Name = 'Software Name'"

I had a similar issue. What i did is as follows:

1. Check if the WMI Windows Installer Provider windows component is installed. If not, install it and try again. If still getting error, go for step 2 and 3.
2. Install Windows Installer 4.5
http://www.microsoft.com/downloads/en/details.aspx?FamilyID=5a58b56f-60b6-4412-95b9-54d056d6f9f4&displaylang=en
3. Install Hotfix for Windows Installer 4.5
http://support.microsoft.com/kb/970553
After a reboot this should work.
I hope this helps.