it seems that when you try to recycle it, it failed to shutdown in certain time, hence the error msgs.
when the user reported the issue, is IIS running? can you browse a simple html page at that time?
what's the error msgs user seeing? what's the IIS log at that time? i'm sure if it is app pool related, there will be event log as well.
You need all these to figure out what's wrong... though my guess is app related.