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User Cant Connect - LimeWire
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Connection problems? Check here first! (click on link)
Probably a firewall issue then.
But sometimes Java 1.6 doesn't work well on some people's systems with a particular LW version. So using the Add/Remove control panel to remove all Java versions & then install this version fixes it:
Java 1.5 (take the JRE)
BTW have you defragmented your computer recently?