Hi Ben,
After v5.0, some API is changed, for example there is no more fileManager.LicenseKey property.
From now on, you should set the license key in one of these ways:
1. Insert following line into the Application_Start method of your Global.asax.vb:
//Set this property only if you have a valid license key, otherwise do not
//set it so FileUltimate runs in trial mode.
FileUltimateConfiguration.Current.LicenseKey = "QQJDJLJP34..."
2. Alternatively you can specify the configuration in <appSettings> tag of your Web.config.
<appSettings>
<add key="FileUltimate:LicenseKey" value="QQJDJLJP34..." />
</appSettings>
As you would notice, FileUltimate: prefix maps to FileUltimateConfiguration.Current
Also from now on, you need to add reference to both GleamTech.Core.dll and GleamTech.FileUltimate.dll found in "Bin" folder of FileUltimate-vX.X.X.X.zip package. Please see this updated KB article for more information (there is the explanation about the other DLLs):