I have emailed X10 about this problem. There has been no response so far, but this might explain your problem:
The issue with the SDK is that the ahscript.dll file supplied in the SDK is version 3.0.0.183 while the version supplied with AHP is 3.0.0.200. The most obvious problem with this is that software that uses the SDK version of the file gets erroneous results when attempting to use the “queryplc” command. Many that have tried to develop software using the SDK have complained that the “queryplc” command always returns a result of 0. Granted this is only an issue if the developer or end user doesn’t have AHP installed, or the developed software accesses a local copy of ahscript.dll instead of the one installed by AHP, but it does lead to a lot of frustration when trying to develop software and the “queryplc” command doesn’t appear to work.