On tuesday, i did a push of a minor front end fix to my rails app.
Since then, whenever rake runs on heroku it blows up like so:

rake aborted!
2011-06-03T08:43:58+00:00 app[worker.1]: uninitialized constant
Rake::DSL
2011-06-03T08:43:58+00:00 app[worker.1]: /app/Rakefile:10:in
`<class:Application>'
2011-06-03T08:43:58+00:00 app[worker.1]: /app/Rakefile:9:in
`<module:Buddy>'
2011-06-03T08:43:58+00:00 app[worker.1]: /app/Rakefile:8:in `<top
(required)>'
2011-06-03T08:43:58+00:00 app[worker.1]: /usr/ruby1.9.2/lib/ruby/1.9.1/
rake.rb:2373:in `load'
2011-06-03T08:43:58+00:00 app[worker.1]: /usr/ruby1.9.2/lib/ruby/1.9.1/
rake.rb:2373:in `raw_load_rakefile'
2011-06-03T08:43:58+00:00 app[worker.1]: /usr/ruby1.9.2/lib/ruby/1.9.1/
rake.rb:2007:in `block in load_rakefile'
2011-06-03T08:43:58+00:00 app[worker.1]: /usr/ruby1.9.2/lib/ruby/1.9.1/
rake.rb:2058:in `standard_exception_handling'
2011-06-03T08:43:58+00:00 app[worker.1]: /usr/ruby1.9.2/lib/ruby/1.9.1/
rake.rb:2006:in `load_rakefile'
2011-06-03T08:43:58+00:00 app[worker.1]: /usr/ruby1.9.2/lib/ruby/1.9.1/
rake.rb:1991:in `run'
2011-06-03T08:43:58+00:00 app[worker.1]: /usr/ruby1.9.2/bin/rake:31:in
`<main>'

I've seen some talk of this on stackoverflow:
in heroku:
http://stackoverflow.com/questions/6181312
in local rails:
http://stackoverflow.com/questions/6085610

For people having this problem locally, it seemed the culprit was the
latest (0.9) version of rake, and downgrading to 0.8.7 solved it.
I've done this in my gemfile, deleted and rebuilt Gemfile.lock and
pushed it up.  In the heroku console i can see that rake 0.8.7 is
installed.  But i still have the same problem so i guess it's not
rake's fault?

Has anyone else seen this or knows a solution?
thanks - max