[horde] Horde 5: IMP will not load

[Bill Day]

I have upgraded to Horde 5 and IMP 6.0.1.  When I try to access my mailbox
I get a "loading" message in the sidebar but no mail appears.  Firebug
gives a long list of error messages, the first few of which I have
reproduced below. I am assuming that I have failed to install something,
but I do not know what.  Any help would be appreciated.  I am running
apache 2.2 on Debian Squeeze with postfix and dovecot.

Thanks,

Bill Day

TypeError: document.observe is not a function
https://williamsonday.org/horde/js/toggle_quotes.js?v=19bbdecfa6ce3c33e1aa42dc000a8eb4
Line 40
TypeError: document.observe is not a function
https://williamsonday.org/horde/imp/js/dimpcore.js?v=f96ff7455f43a9c30f7f28e6cef94c5f
Line 392
ReferenceError: Class is not defined
https://williamsonday.org/horde/js/contextsensitive.js?v=19bbdecfa6ce3c33e1aa42dc000a8eb4
Line 59
ReferenceError: $H is not defined
https://williamsonday.org/horde/js/imple.js?v=19bbdecfa6ce3c33e1aa42dc000a8eb4
Line 20
TypeError: DimpBase.keydownHandler.bindAsEventListener is not a function
https://williamsonday.org/horde/imp/js/dimpbase.js?v=f96ff7455f43a9c30f7f28e6cef94c5f
Line 3846
-- 
Bill Day
williamson.day at gmail.com