problem during com.apple.install with my new Port

[Michael Thon]

Hello - I am having trouble with a new Portfile that I'm writing.   
Here is the relevant part of the debug output:

DEBUG: Executing com.apple.install (hmmer)
couldn't change working directory to "/opt/local/var/db/dports/build/ 
_Users_mike_macports_dports_science_hmmer/work/destroot": no such  
file or directory
DEBUG: Executing com.apple.activate (hmmer)
--->  Activating hmmer 2.3.2_0
Error: Target com.apple.activate returned: Image error: Source file / 
opt/local/var/db/dports/software/hmmer/2.3.2_0 does not appear to  
exist (cannot lstat it).  Unable to activate port hmmer.
Warning: the following items did not execute (for hmmer):  
com.apple.activate
Error: Status 1 encountered during processing.

When executing install, macports seems to be trying to change to a  
directory that does not exist.  However, the directory:
/opt/local/var/db/dports/build/ 
_Users_mike_macports_dports_science_hmmer/work/hmmer-2.3.2/
does exist on my system.  The package seems to compile just fine.
Thanks
Mike