SSL3_GET_CERT_VERIFY:wrong signature size

I am getting the following error in my apache error log when a user is
using their certificate's private key to digitally sign a registration
form on our website. Does anyone know how to fix this so the error
message doesn't appear? The signing algorithm is sha1RSA.

[error] mod_ssl: SSL handshake failed (server www.test..org, client
xx.xx.xx.xx) (OpenSSL library error follows)
[error] OpenSSL: error:14088109:SSL routines:SSL3_GET_CERT_VERIFY:wrong
signature size

I would appreciate any assistance that anyone could give. Thanks!
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