Nick, you can continue to use mIRC after the trial period. It will tell you that it has expired but just wait and it will give you the continue option. I've done that for a while, then I finally paid. :P
I had the same thing happen a number of times, where it would constantly redirect me to the "donation" area instead of connecting. Each time I had to uninstall/reinstall it, and that got old after a few times. I switched to Chatzilla (as said prior), and never had a problem since.