invalid dbms_shared_pool

[AK]

In one of our db i found that dbms_shared_pool package body is invalid . Any idea why that could happen . It's not causing any problem . It's just appearing as one of invalid objects . In fact I am able to execute dbms_shared_pool.keep with out error . Looks like  specification are intact .   there was no package compilation in many days .   Only thing i remeber is , we tried to set keep pool and i misspelled  keep_pool ,( but does that cause invalidation , i dont buy it )   -ak