Hello Jamie,
this is one that has happened for years. It is not a big deal but because I use the feature a lot it happens a bunch to me anyways...
I use the INFO link in the file manager a lot. Sometimes I will open two or three info link windows. But I must click on the "Cancel" or "Save" icon to close... I cannot just click the little "X" in the top right corner.
Sometimes I will get so busy I think I closed it (forgetting it won't close by clicking the top "X") and I will look and see 4-5 webmin windows still open on my taskbar and then have to click through them again by clicking cancel.
Like I said, it's really not a big issue but it has happened for years and I thought you might want to hear about it...
It happens to me using my mozilla browser on the linux box and IE6 with my windows desktop machine.