If you've typed the command and it still doesn't work, try
/localinfo -u and re-do it. You might like to speak to the owner of the Fserve to try to resolve the issue.
Make sure you try
all of the relevant suggestions in the 'Can't DCC Send' thread (where you also posted) and also run a
Search for "dccserver" - lots and lots of threads have been made before about this issue, you might find answers there. Make sure you expand to 'All Forums' and 'All Posts' for best results.
Of course, this message is displayed from FServes meaning you're file sharing. Be careful who you download from, you could be being infected with a virus, you never know what you're downloading until you've ran it. It's a good idea to have 2-3 virus/trojan scanners running, with "auto protect" features enabled if they have it. A few suggestions can be found
here.
Also, heed the warning in
this thread:
"When you accept files from someone you dont know, there's a risk they contain a trojan, virus, or malicious program that can cause a lot of harm. No matter how good/current your antivirus software is, its no quarantee. These things are created nonstop, spread fast, and it takes time for AVs to be updated. Downloading copywrited material such as music and movies also have the same risks, but in addition its against the AUP (acceptable use policy) of some networks and providers and is illegal. When caught you will be subject to lawsuits and huge fines."Happy chattin', good luck and stay safe!

Regards,