Industry standards set by the Certificate Authority/Browser Forum require that all SSL certificates must be at least 2048-bit key length. The deadline to convert 1024-bit SSL certificates to 2048-bit encryption is October 1, 2013.
See http://www.geotrust.com/resources/2048-bit-compliance/ for information on how to move to a 2048-bit certificate.
Contact software.store@vanderbilt.edu if you have questions.