Today I updated my Subclipse, which is my preferred SVN provider for Eclipse. Apparently, the latest version ships with a more recent SVNKit library which requires you to login to your SVN repository over and over again. Other IDE's, like JetBrains' IntelliJ suffer the same problem. To solve this for Eclipse, put the following line into /configuration/config.ini file:
For other IDE's, I guess you can add -Dsvnkit.http.methods=Basic,NTLM to your startup command, not sure though.