problem reading vim online dox

[Aaron Maxwell <amaxwell@phy.ucsf.edu>]

Hi happy people.

In vim, if I type
  :help
I get 
  Sorry, help file "/usr/share/vim/vim56/doc/help.txt" not found
  Press RETURN or enter command to continue
I get this _exact_ same error message if i type any other help command, eg
  :help uganda

The help files are in the vim-rt package, /usr/share/vim/vim56/doc/*.txt.gz
(I'm running potato, vim-rt version 5.6.070-1, vim version 5.6.070-1)

Intriguingly, if I uncompress the doc files (gzip -d
/usr/share/vim/vim56/doc/*.txt.gz), typing 
  :help
yields
  "help.txt" [readonly] 1297L, 61010C
  There is only one matching tag
  File "/usr/share/vim/vim56/doc/help.txt.gz" does not exist
  Press RETURN or enter command to continue
and then it displays the help file!  But if I type
  :help uganda
the response is 
  "help.txt" [readonly] 1297L, 61010C
  There is only one matching tag
  File "/usr/share/vim/vim56/doc/uganda.txt.gz" does not exist
  Press RETURN or enter command to continue
and it gives the general help file (help.txt[.gz]), instead of telling me
how to help Ugandan orphans.

If I have all the .txt files compressed except for help.txt, typing
  :help uganda
yields
  "uganda.txt.gz" [readonly][noeol] 16L, 3666C
  16 lines filtered
  Error detected while processing BufReadPost Auto commands for "*.gz":
  Invalid expression: ":doautocmd BufReadPost " . %:r
  Press RETURN or enter command to continue
and _then_ it gives me the correct help file.  This works, but it's
suboptimal, because next time i upgrade, apt-get won't know to remove the
old help.txt (because only help.txt.gz is in the vim-rt packge.)

Has anyone run into this problem and solved it?
thanks in advance :)

Aaron (in san francisco, land of fog)