Hi Kees,
Thank you for your feedback, how much RAM do you have on your laptops and how many cpus?
Weird behaviuor to say the least, let’s try to get to the bottom of this (since I haven’t seen this happening on any system myself).
I’ll download Linux Mint 17.0 KDE 64bit to see if I can replicate the problem.
I’ll make a virtual machine with the same amount of memory and CPUs.
And, are you using swap memory under Linux?
Mabula