mcrypt_generic_init(): Iv size incorrect

I have an odd php issue with mcrypt. I'm getting a lot of this type of error, but only sometimes: mcrypt_generic_init(): Iv size incorrect; supplied length: 0, needed: 32 (note, the "supplied length: 0" is not always the same. sometimes it is 1, 16, etc). It doesn't seem to affect the decoding of the file, but it is throwing a notice in to my error log. I've tried doing this: @mcrypt_generic_init($this->td, $key, $iv) but that doesn't stop it from throwing an error. The only thing I can think is that I have mcrypt_module_close($this->td) commented out because my code was dying with it... System: Linux w/ Apache 1.3.31 PHP Version 4.3.4 libmcrypt version 2.5.7 Suggestions?