Hello, djill123:
I’m glad restarting resolved the issue. I do recommend double-checking the version as in 10.8.2 there is a -1712 error when formatting, which sounds very similar to what you were experiencing. It’s actually caused by the Mac OS, and restarting would temporarily resolve it. The X6.0.2 version works around that issue, so I do recommend confirming that that update shows in About EndNote window.
As far as inserting multiple citations at once, here’s something that may help – have you considered making groups to organize your large library? If you had a group of, for example, all the citations you plan to use in this particular paper, selecting several at once out of that smaller group would be much easier than trying to hunt them all down in the full library.
Just a thought!
Have a great day.