This is what I received from my ISP:
"Potentially there may be an issue if you are using IRC for downloading or running a file server with our traffic management policies. Alternatively your new LTE has private IPs and NAT enabled that may be causing some issues. Unfortunately at this time we are unable to disable NAT with the LTE service. As there are so many variables involved that can affect the service our customers receive, such as (but not limited to) type of service, level of service package, condition of the computer, use of routers, time of day, number of other users online at the same time, and the type of Internet activity the customer is trying to pursue, we are unfortunately unable to troubleshoot these issues by email."
There's more, but it's just blah blah. For the most part, I don't know what any of that means, but it sounds like they're not going to be of much help in rectifying this. I tried connecting to SSL, but that was a dead end too.
I'll give my ISP a call, but I'm not hopeful for much.
EDIT: Looks like I was mistaken - Hexchat is doing the same thing. It doesn't appear to be happening quite as frequently/regularly, and it's kind of odd that I didn't notice until just now, but it's definitely happening. Not a Mirc-exclusive problem after all, I guess.
Last edited by Malygris; 07/10/15 05:23 AM.