Symptom:

• Error: Can't read from data socket...socket error=#0
  CuteFTP users who were able to make FTP connections previously with no issue, suddenly receiving "Can't read from data socket...socket error=#0" when making an FTP connection. 

Information:

• 3Essentials has found this a problem recently documented on Globalscape's website, the makers of CuteFTP...
• http://forums.globalscape.com/tm.aspx?m=21189&mpage=1&key=&#21204
• http://kb.globalscape.com/article.aspx?id=10472
• These resources mention that this issue can be caused by malware on the user's system.  If you read through the forum postings, you'll see that this malware can also affect other things, such as the ability to open a command prompt.  With that being the case, it possibly may affect other FTP clients as well, although the symptoms may present differently.