v6.0A no longer compiles my VC NEt projects

[P. rolling]

My script worked fine under 5.7. I upgrade to 6.0A and I get this now:
"
Building project step 'Make VS.NET'...
Error creating custom action 'Make VS.NET': No such interface supported
Step 'Make VS.NET' failed
Build ended.
"
Below is the 5.7 VC NET step that fails in 6.0A:

====

<step action='Make VS.NET'>
<Attr type='11'>0</Attr>
<Config>Release</Config>
<FileVer type='11'>-1</FileVer>
<Filename>%PROJECT_DIR%\PlugInManagerDriver.sln</Filename>
<Force type='3'>1</Force>
<ShowCmd type='11'>-1</ShowCmd>
<condcompareto>1</condcompareto>
<indent type='3'>2</indent>
<name>Build all modules in Release mode</name>
</step>


<macro name='PROJECT_DIR'>
<value>E:\PBProjects\PI\PR_PI_Harness_3.00.00_Priv \PIMC_TestHarness\Dev\PlugInManagerDriver</value>
</macro>

What has changed from 5.7 here?