In order for us to help you, you will need to post what error message you are receiving. Make sure you read all the posts in this thread and see if anything applies to you. Also include:
1) What version of mIRC you are using.
2) What Operating System (95, 98, XP, ME etc) you are using.
3) If you have any Firewalls installed.
4) If you are using a router, and what make.
Also make sure you read the Common IRC Errors
post and run a Forum Search
. With the search feature make sure you expand to 'All Forums' and 'All Posts' for best results - also make sure you use concise search terms.
Finally, make sure you try to connect to multiple servers/networks to see if it's a problem with a specific server/network or if it really is "anything".