Access SVN slowly at first time login

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Dear:
    I have a question when using SVN. Could you please help me on this?
    We run two SVN virtual machines(with Windows Server 2003 system installed 
Subversion Edge ) on the same physical machine.We set LDAP authentication both 
on the two virtual machines.When we log in SVN at the first time, it behaves 
slowly, and after I closed SVN log-in widows mandatory, and log in SVN again, 
it behaves normally.
    Looking forward to your reply!