As you mentioned the applet is only executed when the send button is pressed. The send event is unrelated to the new message arrival event. I don’t think DoEvents() will make a difference in this scenario.
I am at a loss to explain why you might see this behavior. I am aware of large numbers of users using applets integrated on send that have not reported this type of problem.
You mentioned your applet is ‘rather complex’ – what does it do? The only scenario I can think of is that your applet is somehow ‘hogging’ resources, slowing the main processing thread of the GroupWise client.
Unfortunately I suspect you’ll have to undertake a process of elimination. For example, what happens on these machines if you install a simple applet, integrated with the On Send event, but does nothing else? Does the problem still occur? If not, what action is your applet taking that might cause GroupWise to behave this way?
Please let me know how you proceed.