In the past I had received this message and even went so far as to reinstall PCAnywhere, but to no avail that failed miserably. The first time I got this I said, "I'm boned" and did many Google searches. I came across a post that was completely unrelated to PCAnywhere, but had a brief message about CryptoAPI. I have long since lost this url, however the answer is still fresh in my mind. It turns out that PCAnywhere Symmetric encryption relies on RSA info located at:
c:\documents and settings\[USERNAME]\Application Data\Microsoft\Crypto
This folder contains another folder called "RSA" . To fix your problem, just rename the folder (or delete it, but better safe than sorry if something else breaks - you have been warned!). The next time you launch PCAnywhere and try to connect to a server, the RSA folder will be recreated and you will be all set!