[TxMt] man pages in TextMate

I notice that for certain commands the 'Documentation for word / Selection (man)' is unable to find the man page for some commands while typing 'man foo' seems to work.

For example 'asr' returns the man page formatted quite nicely in the html window.

However on my system (MacBook Pro, running 10.4.6 w/dev tools, and cutting edge TextMate) the documentation for hdiutil and rsync couldn't be found.

Do I need to modify my shell configuration? or the command in someway? My apologies if this has been discussed before, briefly searching the list didn't seem to turn anything up.

Thanks

Peter