Permissions problem

[Vince Rice]

> uname
Darwin SRSMBPRO.local 9.5.2 Darwin Kernel Version 9.5.2: Thu Oct  2 14:51:59 PDT 2008; root:xnu-1228.8.59~2/RELEASE_I386 i386

> sw_vers
ProductName:Mac OS X
ProductVersion:10.5.5
BuildVersion:9F2533


> port -v
MacPorts 1.700

Xcode is 3.1.2 from the Xcode/About menu.

All steps below performed from an Administrator login.

I installed port itself by downloading the .dmg and running the Installer. That created the /opt/local/* directories and added them to my path, etc. I then ran
port -v selfupdate
without incident, i.e. no errors and it said it had nothing to update.

However, trying to subsequently install any package is giving me permission denied messages on /opt/local/var/macports/build. The exact error message is:
Error: Unable to execute port: can't create directory "/opt/local/var/macports/build": permission denied

A quick ls of the /opt/local/var/macports directory shows:
drwxr-xr-x   8 root  admin  - 272 Dec 21 16:41 macports/

So, it's owned by root, and none but root has write access to it. Is this normal? Is there something else the Installer should have done to allow write access? Are the directories supposed to be owned by root? Are they supposed to have write access? What went wrong, and what do I need to do to fix it?

I checked the FAQ and didn't see anything related to this.

Thanks!