CVS - ProxyHTTP: java.io.IOException

Problems reported while synchronizing CVS Workspace. 0 of 2 resources were synchronized.
  An error occurred synchronizing /a_proj_3.0/src/운영_serverConfig.properties: Could not connect to :pserver:user5@1.2.3.4:/cvs: I/O exception occurred: ProxyHTTP: java.io.IOException
    Could not connect to :pserver:user5@1.2.3.4:/cvs: I/O exception occurred: ProxyHTTP: java.io.IOException
    ProxyHTTP: java.io.IOException

IE에 프록시 설정을 했더니 이클립스에서 CVS 저장소와 동기화하면서 발생한 에러