Many times I had this issue which could be solved only by rebooting.
Today I got more smooth solution (but anyway it's a bug from Apple).
-- it turns out that behind the Character Viewer placed a dialog box about downloading an extra font and it's waiting of your permit (but you can't see that). So moving Character Viewer to any side you'll see that dialog on the screen, you can provide your decision and you don't need to reboot your machine.
MacBook Pro 13″
NEBOBROD wrote:
Many times I had this issue which could be solved only by rebooting.
Today I got more smooth solution (but anyway it's a bug from Apple).
-- it turns out that behind the Character Viewer placed a dialog box about downloading an extra font and it's waiting of your permit (but you can't see that). So moving Character Viewer to any side you'll see that dialog on the screen, you can provide your decision and you don't need to reboot your machine.
insightful post NEBOBROD
you can file a bug report /submit your Apple Feedback here: Product Feedback - Apple
Character Viewer hangs on Macbook
