Stored procedure arguments get immediately truncated
MySQL timestamp is not a Unix timestamp.  It has the form '2012-02-02 12:12:12'.  I think it is worth to mention that it differs from datetime in that while timestamps minimum and maximum values correspond to that of a Unix timestamp, datetime has a broader range.

See the docs here:
http://dev.mysql.com/doc/refman/5.5/en/datetime.html

The easiest solution is changing arguments to integers.  The other way is of course producing valid timestamps in the calling application and feed those to your stored proc, but in this case you will have to modify the proc as well (by removing the FROM_UNIXTIME conversions).  (Thanks for DTest for the suggestion.)