Running into the Great Firewall of China

I access data from public Chinese webservers for some of the data I present on this blog.  During the start of the Google/China controversy I began to notice some odd 'errors' as I attempted to access Chinese web servers.  Sometimes I get a simple 'hello!' from the server and nothing else, other times I get a 404 error and other times there is no problem.  

I wonder if the 'Great Firewall of China' as described by the WSJ is working on keeping away the outsiders as well? 

China generally doesn't tell its people when it is interfering with their Web access, unlike some other countries, such as Saudi Arabia, that give explanatory warning messages when users are denied access to forbidden sites.

Instead, China's filtering can look to users like a technical glitch—an error message in a user's browser that makes it seem like his connection to the Internet malfunctioned. Authorities don't discuss the methods or tools they use.

Anyone else running into the same issues? 
Here's one test I just ran:
http://www.pbc.gov.cn/  -- Returns 'hello'
 
http://www.pbc.gov.cn/english/ -- Gives me a 404 error (page not found)
 
Both of those sites have worked on and off for a week or so. If you do a Google search for "people's bank of china" these are the first links you get and the Chinese central bank is not an obscure web site I'm hitting.  There's others web sites that return the same errors... puzzling . . . .

[edit 04/05/10 11:20am pst: I was able to access the above web sites on Saturday and pull the data I was looking for.  Today, Monday, I was unable to do so and received the same error messages.  I'm going to get a packet sniffer and see if the error message / 'hello' comes from the same location as the normal data and see if the Great Fire Wall is somehow blocking me ]