Ruby/Rails OpenSSL::PKey::RSAError: data greater than mod len

I think I started getting this error when I switched from MySQL to PostgreSQL.
I had written code to encrypt decrypt model attributes containing sensitive data and I had it working until the db switch.

I have the following code:

@pbk = OpenSSL::PKey::RSA.new File.read("#{RAILS_ROOT}/cert/pb_sandwich.pem")
@pvk = OpenSSL::PKey::RSA.new File.read("#{RAILS_ROOT}/cert/tuna_salad.pem"), 'pass45*'
model.sendata = Base64.encode64 @pbk.public_encrypt(model.sendata)

I run that code on save. I've also tried with and with out first using Base64.

Then when I try to read:

@pvk.private_decrypt Base64.decode64(model.sendata)

I get this error:

OpenSSL::PKey::RSAError: data greater than mod len

I never got that before when I used MySQL. I can't really remember what datatype the sendata column was in MySQL but in my current PostgreSQL setup that column is datatype `bytea`

I'm assuming that is the problem since it used to work fine with MySQL. What datatype should the column be if I wanted to skip having to do that extra step to Base64 encode/decode? If that is the problem that is.

Another thing of note is that I've tried generating the private key with mod lengths: 2048, 4096, and 5120 and I always get the same error. Also, the sendata field isn't very long before encoding, it's under 40 chars.

I'm stumped right now, any ideas?