Question regarding post size limits ssl?

Brand new to this email list.  I have a question.  There is a secure 
site we are trying to post to.  The post data can be quite large as it 
includes an entire urlencoded html file.  Sometimes it works fine but 
sometimes it just hangs and eventually times out?  I did read somewhere 
that over ssl there may be challenges with sending larger posts?  We are 
using php curl commands i.e. curl_exec but from the command line here is 
the version information (I am assuming php uses the same version but not 
sure)

curl 7.12.1 (i686-redhat-linux-gnu) libcurl/7.12.1 OpenSSL/0.9.7a zlib/1.2.1.2 libidn/0.5.6
Protocols: ftp gopher telnet dict ldap http file https ftps 
Features: GSS-Negotiate IDN IPv6 Largefile NTLM SSL libz 

php version is 5.0.4, CentOS Linux 4.7 is server os/version.

Any ideas or thoughts about why this may be happening and how to fix?  Should we upgrade the curl version?

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