I tried FroggieDaFrog's version, but same error.
I'm not able to reproduce this. The socket reply you get is weird (i.e. the "location: nnscript" thing - yet I cannot think of how nnscript could interfere with the setting of &a in the sockread event). Does the error always contain "content-length: 0"?
On connect it shows
* [GetIP] Resolving your IP address...
* [GetIP] Error parsing socket reply: Date: Wed, 06 Oct 2010 14:38:11 GMT
And if I do /getip manually. I gethttp://www.whatismyip.com/automation/n09230945.asp
shows my correct IP. It's same like on wieistmeineip.de. I am sure it's the right one, because if I set it manually everything (like dcc chat with eggdrop) works.
What mIRC version do you use?