anyone can help??? when i log in to dalnet it show as below :

-matrix.dal.net- *** You are banned from DALnet
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-matrix.dal.net- *** Reason: [AKILL ID:1344212893K-a] [exp/ma] You are infected with an IRC trojan/virus. Visit http://kline.dal.net/exploits/akills.htm#ma (2012/08/05 17.58)
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-matrix.dal.net- *** Connection info: <unnamed>([-]unknown@183.78.38.174) [183.78.38.174]
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-matrix.dal.net- *** Ban contact: kline@dal.net
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-matrix.dal.net- *** When contacting DALnet, please include all of the information shown above
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A-banned: [AKILL ID:1354232994K-a] [exp/ma] You are infected with an IRC trojan/virus. Visit http://kline.dal.net/exploits/akills.htm#ma (2012/08/05 17.58)
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Closing Link: 0.0.0.0 (A-banned: [AKILL ID:1344212893K-a] [exp/ma] You are infected with an IRC trojan/virus. Visit http://kline.dal.net/exploits/akills.htm#ma (2012/08/05 17.58))
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* Disconnected

but i did a anti-virus scan with latest update, but it still the same!!!what the problem and what should i do???

Go to the Dalnet website and email them about the problem. Usually what happens is someone else with an IP very similar to yours (probably also from your ISP) wss banned and the ban included multiple IPs including yours.

I did post it in Dalnet web page and inform them last night, but until now still don hv any reply!!!

They maybe get 1000 mail during a day/evening, you need to wait, i guess it can take up to 1 week until a answer..

Probably not a week, but you do have to wait. There's nothing anyone other than Dalnet can do for you at this point, so wait until they resolve it for you or use another network.