Steps to reproduce:

1. Create a web test.

2. Add a coded step: ActiveBrowser.ClearCache(BrowserCacheType.History);

3. Run it against FireFox.

Expected: The history is cleared.

Actual: 

ArtOfTest.WebAii.Exceptions.ExecuteCommandException: ExecuteCommand failed!
InError set by the client. Client Error:
mozCommandProcessor: TypeError: Components.classes['@mozilla.org/browser/global-history;2'] is undefined
BrowserCommand (Type:'Action',Info:'NotSet',Action:'ClearHistory',Target:'null',Data:'',ClientId:'55f0e69a-572e-4b47-b2af-2fd284ed4f27',HasFrames:'False',FramesInfo:'',TargetFrameIndex:'-1',InError:'True',Response:'mozCommandProcessor: TypeError: Components.classes['@mozilla.org/browser/global-history;2'] is undefined')
InnerException: none.

is thrown.