Installshield .NET framework problem?

Question

We have developed a scan to pdf package, see www.scantopdf.co.uk, and as of last week we had an installshield generated installation that was 1.51Mbytes and only downloaded and installed dotnetfx.exe if required. This week we have noticed that the same install program not only installs dotnetfx but also downloads and installs another microsoft program which is 10.45Mbytes. The .NET install then seems to spend forever configuring .NET, eats a few hundred Mbytes and requires a reboot prior to installing our software. We can't tell what the second Microsoft download program is becuase the URL is obscured (see install1.jpg and install2.jpg) So in summary; we haven't changed our install program, but now it downloads an extra 10Mbyte Microsoft installation file, takes much longer to run and requires a reboot. Installshield and Microsoft support are not interested; here's hoping one of you guys can shed some light.