curl works but ping/urllib2 don't, in a virtual machine

Question

I have a Crunchbang 10 VM running on VirtualBox on a Windows 7 Home host. I have a python script that uses urllib2 that was failing, and discovered that: ordinary browsing and curl work normally on the VM, but ping and the urllib2 requests to the same (and any) sites fail.

ping says: ping: unknown host http://www.google.com/

urllib2 raises a URLError to the same effect. Are there any reasons this might be so, and how might I further investigate get ping (or even urllib2) to behave? Windows Defender firewall on the host, don't think any firewalls are running on the guest. Behavior does not change using either NAT or bridged networking.