Questions about command line builds

First off if this is not the place to ask apologies. My company recently upgraded to TFS 2012. Previously we were using setup projects within our solutions to build out our msi's. 2012 no longer supports our previous method and gave us a link to Install Shield. The version we are trying is the 2012 Spring Limited Edition. From within visual studio things are working fine for the most part inside of TFS (minus a random com removal error that we have to run TFS in admin mode for). However we previously used nant and some build scripts to do our daily builds. One of our solutions (the same one with the com problem) gives me the following errors when I build via my scripts.

[msbuild] "C:\ALPHATFS\ExternalInterfaces\ExternalInterfaces.sln" (default target) (1) ->
[msbuild] "C:\ALPHATFS\ExternalInterfaces\RandomServiceInstaller2\RandomServiceInstaller2.isproj" (default target) (13) ->
[msbuild] (Build target) ->
[msbuild] C:\Program Files (x86)\MSBuild\InstallShield\2012SpringLimited\InstallShield.targets(96,3): error : Failed to load ISWIBuild: -2147221164
[msbuild] C:\Program Files (x86)\MSBuild\InstallShield\2012SpringLimited\InstallShield.targets(96,3): error : Exception Caught
[msbuild]
[msbuild]
[msbuild] "C:\ALPHATFS\ExternalInterfaces\ExternalInterfaces.sln" (default target) (1) ->
[msbuild] "C:\ALPHATFS\ExternalInterfaces\RandomServiceInstaller3\RandomServiceInstaller3.isproj" (default target) (14) ->
[msbuild] C:\Program Files (x86)\MSBuild\InstallShield\2012SpringLimited\InstallShield.targets(96,3): error : Failed to load ISWIBuild: -2147221164
[msbuild] C:\Program Files (x86)\MSBuild\InstallShield\2012SpringLimited\InstallShield.targets(96,3): error : Exception Caught

I did find a thread on these forums that this was most likely due to the fact that I already built one installer in the solution and that the dll was still in memory. I have no problems removing them from the build manager and building them separately one at a time, but I can't seem to find a way to build the isproj files from the command line. I found mention of a ISCmdBLd.exe but I can't find that anywhere on my machine. Is that only available with a different version of Install Shield? Is there a work around that I can use?

Sorry for what may be the information overload, just wanted to try to give as many details as possible.