I have a Server hosted FM12 solution that works fine with FM and FMGo but was causing me significant hairloss on account of several buttons seemed not to work in IWP. I now suspect that a script step to a layout name that starts with an underscore ('_') will fail catastrophically in IWP on Safari 5.1.7 or Firefox 18.0.2 on OS X 10.7.6. And that is regardless of setting Error Capture 'ON' or Allow User Abort 'OFF'. Certainly, once I renamed the layout and without any other change, a button previously inactive in IWP now works as expected.
I can find no mention of this difference in the IWP Guide for FMP12. And I can't report it as a suspected bug because the .co.uk bug report page doesn't offer FM12 in the popup and the .com bug report link I have used in the past now points to these forums
Can anyone corroborate this problem, and assuming it is a real issue, does anyone know of any other undocumented gotchas in respect of IWP?