I've been unable to use my Dictionary App for a few days, as it consistently says that it is downloading the dictionaries. I can't find out why it started downloading them again (it already had them), or how to check on the state of a download, or where it is downloading from. I am at a loss as to how to diagnose this. Any ideas?
I've experienced this problem once in a while, and find that it's due to the DictionaryServiceHelper process freezing. To fix it, first I quit Dictionary, and then I open a terminal and type:
pkill -9 DictionaryServiceHelper
Yes, you really do need to send the dangerous SIGKILL (signal 9) in this case.
If you're not a command line person, you can alternatively open Activity Monitor, search for DictionaryServiceHelper, and force quit it.