apt-get reports ridiculous expected time for completion

I am on 64-bit Ubuntu Karmic.

Sometimes when using apt-get, the program reports a very large
estimated time remaining.

For example, today apt-get reported that upon performing sudo apt-get
update, it will take 213503982334601 days, 6 hours, 59 minutes and 22
seconds to complete. This is roughly equal to 40 times the present
estimates of the age of the universe.

At the time that apt-get reported this expected completion time, it
was downloading at 3161 bytes per second, so it seems unlikely that
the calculation is correct. If it is correct, it is of no practical
value for apt-get to do this.

I am pleased to say that my download completed without incident about
a minute later.

Richard