Network calendars not showing up on reload

I'm using Sunbird Portable with iCal Exchange (icalx.com), and though it's worked previously, I'm now having trouble now with my network calendars.

When I subscribe to a calendar hosted on iCalx.com, all the entries show up perfectly. However, when I exit Sunbird and reopen, nothing shows up. When I tell Sunbird to reload my remote calendars, it sits and thinks for a bit, but nothing happens. If I disable one of my remote calendars, oddly, the data from my local calendar disappears.

I've deleted the data folder and re-imported it all, and when that didn't help, I deleted and reinstalled Sunbird, with no change.

Other useful info- my University's network requires use of a .pac proxy configuration file (which I've set up correctly and reloaded). Any ideas?