I am also a long time user of CCleaner with never the slightest problem so expected smooth sailing with Speccy. However, it seems i've had a similar experience to a number of other people, in that it caused my computer to completely lock up. I could not even Ctrl+Alt+Del to end the task, or turn off the computer. The only way I could get the computer to turn off was by pressing and holding the power button.
It seemed to be getting hungup on reading the RAM and hard drive.
I noticed that i was using an earlier version (1.03) so i uninstalled it and installed the latest version 1.04 however the same thing happened...although it did read the RAM and hard drive before freezing. Also this time when i tried to press some keys on my keyboard the computer made a loud scary beep. I had to do a hard shutdown using the power button again. This time when the computer restarted Windows automatically ran the chkdsk utility.
Something is clearly not right. I am running an HP laptop with windowsXP freshly re-installed, so the system is very clean. The only system monitors im running that could potentially interfere are Prevx and WinPatrol, but neither made a noise.
If there are some logs or error reports or other information that you would like me to provide that could help you debug please let me know soon, because i plan to uninstall the software.