On August 20th I installed a 64 bit
distro with kernel 3.3.8 and KDE 4.8.5
, no more problems since that date, the host did not freeze anymore. I use same VMs, the Win7 and the 32bits LXDE PCLinuxOS, everything is working smoothly.
I have learned a big and costly lesson, I should trust in my first thoughts, when I purchased this new machine, I thought I needed a 64bits OS.
I will continue using PCLinuxOS but for the VMs until the release of the 64 bits KDE.
Thank you very much for your patience and time to answer all my questions.
PCLinuxOS Forum is the best
forum and community I have ever seen