As you said that you are end of you trial period, So may be this is why some of your workstation are unable to install applications pro version…
Just make sure you are not running av scans during the day in your profile. Also, open task manager and check what part of XIG(av) is using the most CPU/Disk). I find my performance issues are when they run scans on slow machines. Also, open task manager in comodo av it self and see if any thing is running.