Error -15000 when trying to play to Airport Express speakers

For some reason, this got marked as "solved," when in fact it is nothing of the sort.

I've got a new Dell laptop (Dec. 2013) that came with Windows 8 installed, although I quickly updated to Windows 8.1 During that time, iTunes has never been able to connect to my Airport Express speakers. I used them just fine with my old computer under Windows Vista and Windows 7.

Until yesterday, whenever I tried to connect to a speaker, the program would pause for about 30 seconds, then give me the dreaded -15000 error.

Later yesterday I reconfigured my firewall (McAfee LiveSafe Internet Security) to not only allow iTunes to do whatever it wants with the network, but also to specifically open TCP and UDP ports associated with iTunes in the hopes of getting it working.

Now it doesn't give me the -15000 error, but it fails silently (without a popup). It doesn't connect to the speaker, but just leaves me with the computer speaker selected.

I've also removed McAfee entirely, rebooted several times, and it still didn't work. The same problem happens with a tablet PC running Windows 8.1 and using the Windows Firewall. That tablet happens to be a Dell as well. Maybe a Dell IPv6 problem?

Another possibility: my Airport Express Speakers are all First-Generation - is it possible that the First Generation Airport Express doesn't work with Windows 8.1?

I also used Wireshark to watch my connection to the speaker. After it gets the IP address of the speaker using MDNS, itt connects on port 5000. The connection to port 5000 does nothing for about 30 seconds, then closes. During that 30 seconds, iTunes keeps sending around MDNS queries for QM but I think that's Home Sharing. Then it gives me the -15000 error. Ideas?