cabal-install fails on WinXP

I've tried using cabal-install (cabal.exe) for the first time to install yi, and all of the packages fail to download. Reducing to a simple test case, "cabal install binary" fails with: Resolving dependencies... Downloading binary-0.4.4... cabal: Error: some packages failed to install: binary-0.4.4 failed while downloading the package. Where do I look to diagnose this? Alistair