Hi Neil! Welcome to our forum!
First, make sure that you have installed all windows updates on the computers. Missing updates are often a cause of computer misbehavior. Note that you will need to press the check for updates button manually, then install any updates, then restart the computer, then check again. Some updates are not offered, if you do not install the previous update first. You need to do this until the computers are fully updated.
Next, check whether you still have installed other security programs, which may conflict.
Last but not least, if neither of these two are the cause of your issue, please contact us via Live Chat or email at support@bullguard.com and we will assist you, free of charge, to check for any other possible causes for your problems.