What Subversion server distribution do you use? What is the version? If you use an up to date VisualSVN Server version, the problem most likely will not occur. If it occurs, try re-importing the certificate again - modern VisualSVN Server versions build a certificate chain automatically when you import a certificate.
[[[
intelli4m.com has a trusted chain containing an
expired certificate. This chain will work with modern web browsers (they will use a chain to a different trusted root) but
may fail with older clients, notably OpenSSL 1.0.x.
]]]
You can also find more details on the problem on the following pages: