Vista domain member computer with slowness when off the corp netwo

Can someone please explain to me why my laptop which is a member of our
corporate Active Directory domain seems to have slowness issues at home when
not connected to the corporate LAN?

Here are two clear symptoms that appear to be directly related to this
because when I connect to the corporate network at home via a Cisco VPN
client, neither of these symptoms persist:

(1) When I am browsing the Internet, for example, and am trying to save a
file, Explorer opens and takes a significantly long time to show me my
"default view" of folders... (doesn't happen when using VPN client -- they
pop right into the window)

(2) When I am using Internet Explorer, I have to type in http:// before any
URL. If I don't, it's almost exactly 30 seconds after typing the URL that IE
will eventually open the Website I typed in. Again, this behavior is not
replicable when I am using the VPN client with "domain connectivity."

I would love to know if this is a "bug" in Vista that will be fixed or
whether there is a "hotfix" available that addresses this "symptom." I can
reproduce this on multiple machines that are members of the corporate AD
Forest and exhibit this behavior immediately upon connecting using an
Internet connection that does not have access to the corporate domain (i.e.
using cached credentials).

Thanks in advance for any assistance in understanding (and hopefully
resolving) this unwanted behavior.