Tried to google your error and found 2 possible solutions.
First try this one:
.net - loadFromRemoteSources error using Assembly.LoadFrom - Stack Overflow
The first answer. Go to properties of the dll file (Plugins/Webstats/WebStatsPakets.dll) and see if theres any unblock button.
If this doesnt help, try to edit your DemonBuddy.exe.config file and add
<runtime>
<loadFromRemoteSources enabled="true"/>
</runtime>
between the <config> </config>
If i added it to mine, it would look like this:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<startup useLegacyV2RuntimeActivationPolicy="true">
<supportedRuntime version="v4.0"/>
</startup>
<runtime>
<loadFromRemoteSources enabled="true"/>
</runtime>
</configuration>
One of those should hopefully help