Which version of IGB are you using? I will see if I can reproduce the issue on my Mac.
To get the IGB version: In the IGB menu bar > click IntegratedGenomeBrowser > then click About IntegratedGenomeBrowser
If you could also attach the IGB logs that would be great.
Click on the Log tab > then click on Copy All To Clipboard (can paste into a reply).
Thank you for reporting this issue!