CI 1.6 >> Error when trying to decode using Encrypt library in PHP4.4.7

[eluser]stevepaperjam[/eluser]
I'm not using the encrypt functionality in my app, but I created a quick test controller to see what would happen, using the example from the manual pretty much verbatim, and it seems to work fine.

I encoded "My secret message" without a key, and got (deep breath)

ooMeKjNhz9mNX2mOMNvSELW1ppkuo1jASBMgaxPasOZdsKXIfUpu/sEZvXig6lC72LCLPre2FiBabUhJgRr0K3N+ihNEGv8VGfF2lp0H7U6BWGZtvt/ICFbfa5e634wO

Slashes and all. Decoding this behemoth got me "My secret message" back again.

Refreshing my page got me a different encoded version, but after decoding again I always got "My secret message" back at the end.

I'm still on PHP4.something because my (reliable, but dull) provider won't change. I haven't tried it on PHP5, I could flip to it and see how that works.