If you have Internalz, check /var/usr/lib/ipkg/lists/ and see if one of the files is very big (like over 100MB). If so, delete that. Something in a patch or an older version of Preware/Package Mgr Service right after 1.3.1 seemed to go crazy with a feed. Hasn't happened in a couple days for me now, though, so I think new versions are fixed.
See this thread