Did a bit of digging around, and many other web sites are being bit by this as well. The nerd details...it's specific to a very common way that javascript is used to open popup windows. This method is used by the photo gallery we have installed.
Unfortunately, the permanent fix lies with Apple - a bug was introduced into Safari with a recent OS X update that is the culprit. Previous versions of Safari worked fine, and the Windows versions of Safari are not affected either. There are coding workarounds that some sites have implemented to get around the bug, but I won't be putting them in place at the C-Brats. It's simply too much work and risk for too little return, to fix a problem that Apple should rightfully address.
Were there not alternatives for our Mac users, I might reconsider...but given that other Mac browsers work fine, I'd prefer affected members use those options until Apple fixes things on their end. Given the number of sites reporting this issue, one would hope it would be a high priority for them.