Text filter problem migrating from 4.03 to 4.1

I’m having trouble migrating from typo 4.03 to 4.1.

Specifically, the typo:code…</typo:code> syntax filter isn’t
working properly for me at 4.1.

When I look at the rendered HTML, it shows something like:

...

I.e. the syntax filter hasn’t been applied for some reason.

What’s really perplexing is that this same migration worked just fine
when I practiced at home. There are plenty of differences between my
home and shared server setup, and I don’t really know where to start
looking for a solution to this one.

Inspecting the CHANGES-4.1 file suggests things have changed in this
area.

Any pointers gratefully accepted. (But note my hands are somewhat tied
on the shared server – it’s not meant for doing development work).

The most relevant looking section of the production.log reads:

Processing ArticlesController#permalink (for 87.80.246.57 at
2007-06-11 08:06:36) [GET]
Parameters: {“month”=>“04”, “title”=>“high-altitude-programming”,
“action”=>“permalink”, “day”=>“13”, “controller”=>“articles”,
“year”=>“2007”}
Filter chain halted as
[#<ActionController::Caching::ActionParams::ActionParamCacheFilter:0x9b0f3fc
@actions=[:index, :read, :permalink, :category, :find_by_date,
:archives, :view_page, :tag, :author]>] returned false.
Completed in 0.08282 (12 reqs/sec) | Rendering: 0.00011 (0%) | DB:
0.00000 (0%) | 304 Not Modified
[http://blog.wordaligned.org/articles/2007/04/13/high-altitude-programming]

Thanks in advance,