Can't Switch to SQL Authentication (Mixed Mode)

We have a SQL installation that was setup with Windows Authentication.
The software we will run requires SQL Authentication (Mixed Mode).
When I right click on properties, go to the security tab, click the SQL
Authentication, click on OK and it exits. However, when I go back in
and look at the security tab, it is still set on Windows
Authentication. I tried restarting the SQL services and I get the same
thing.
Ideas?
I have resolved this issue by logging in as the domain admin. I had
previously tried using a local admin account.
jd
JohnDoe wrote:
> We have a SQL installation that was setup with Windows Authentication.
> The software we will run requires SQL Authentication (Mixed Mode).
> When I right click on properties, go to the security tab, click the SQL
> Authentication, click on OK and it exits. However, when I go back in
> and look at the security tab, it is still set on Windows
> Authentication. I tried restarting the SQL services and I get the same
> thing.
> Ideas?