Hi Paul and David,
I've undertaken some testing on my Windows 7 32-bit PC (works fine) and a Windows XP (32-bit) PC (software freezes at random) using PicoLog 5.22.4 and a direct serial connection.
This is most likely due to the fact that the device is not receiving enough voltage under load conditions (7V) and therefore we recommend the use of a USB-Serial converter. We do sell one that we know is compatible with the device:http://www.picotech.com/usb_data_acquisition.html
Within PicoLog, you would have to select the COM port corresponding to the USB-Serial connection (this will be shown in the Device Manager)
For Windows XP or later, drivers would have to be downloaded from our website. You can also try an equivalent cable if you wish.