Windows Installation does not work recently

I have executed several Windows-Installations in my Company: iMac 2009, Mac MIni 2010, Mac Book Pro 17", Mac Book Air. XP and Windows 7. SSD and HDD, on Partition and Windows without Bootcamp on the whole HDD.

This Week i want to repair the Windows 7 U on the Mac Mini (because of Disc Failure). But the Installation freezes on the first GUI-Screen, the one with the Language.

I tried Installation from CD-ROM and USB, with and without BootCamp Drivers – Freeze.
So i thought the Mac Mini is defect.

But i tested the USB-Stick and the CD-ROM on other Macs: same Phenomenon: Freeze.

I tested different USB-Keyboards and MIces, the internal on Mac Book Air – Freeze.

The Common characteristic of these Macs are System 10.10.3 – can this be the Problem?

Any Ideas where the Problem is?

P.S.: sorry for my cruel English