As Tim already indicated, I think it should be " instead of %22
Also, this error seems to suggest that the client is having an issue finding “__Download\BluStarClientSetup.exe”.
I would double check that this file exists as it should and try running it from the command line directly to see what happens. Also try it using PSExec.
I had something similar happen last week, with a BroadCom BASP installer. I think that there is something odd with command-line parsing for particular InstallShield-based installers, where BESClient gives this error if the command-line parameters contain doublequote characters; but I’m not at all certain on that count and I will probably not be putting much more effort in to it.
In my case, we worked-around the problem by using appendfile to create a batch file to contain the installation command, and using waithidden to execute the batch.