Hi, I'm experiencing the same problem here. The locale is the same on the client and the box running apt-cacher. They're both running testing.
The box running apt-cacher is updated daily while the client is generally updated once a week. Problems began to appear some days ago, after testing began to thaw (sorry, I can't be more precised, didn't took note since I thought it was some network problem as they were transient problems then and the network at work is somewhat strange lately). As a matter of fact, apt-cacher was upgraded from 1.6.4 -> 1.6.7 on February, 23rd and this seems to me to be that the problem started to appear erratically approximately at this moment. First, the box with apt-cacher began to exhibit the problem from time to time (maybe twice a week) but it disappeared when re-running 'aptitude update' and last week-end the same problem exhibited while connecting to apt-cacher from the remote client (yet I managed to get to update re-running the aptitude command at once). But tonight, at home where the network has not been twiked recently, I've been completely unable to update the client until I used the workaround given by Raphael (Acquire::http::Pipeline-Depth "0" - many thanks, Raphael!). Aptitude always failed on the testing-proposed-updates/contrib line. As you suggested, I turned debugging on in apt-cacher and ran aptitude with the Debug::Acquire::http=True option. The log file is attached to this mail. HTH pp
error.log.gz
Description: GNU Zip compressed data
