Google Voice VOIP Weirdness

From time to time, I use Google Voice to make free phone calls anywhere in the United States. Typically I access Google Voice through Gmail via a desktop browser by clicking the "Make a call" link in the far left column in the Gmail interface, pictured here:

From there, I enter the area code and phone number that I need to call. Since some of my calls are web conferences, I often need to enter an access code to join a meeting. While I've never had a problem placing domestic calls, lately I've had some difficulty entering passcodes into Google Voice, and although I do not understand the root cause of the problem, I have been able to reproduce the issue.

Upon invoking Google Voice via Gmail, the calling interface is displayed at the lower right corner of the same browser window where my Gmail contents are displayed:

From here, I am able to successfully enter audio conference passcodes, both by clicking on the numbers in the keypad as well as typing the numbers on my physical keyboard.

However,  when I click the arrow at the upper right to open up the calling interface in a new window (which I often do so that I can have 2 open browser windows to look up my passcodes), the numbers do not consistently register. This happens both when I attempt to click the numbers on the keypad and when I attempt to type the numbers on a physical keyboard. The numbers that do register are delayed by about a few seconds which usually results in a failed entry when I have several digits to enter.

At least I know how to work around the issue by not opening Google Voice in a new window until AFTER I successfully enter my passcode. I think Google Voice is a great service, and if you've been plagued by the same issue, I hope this helps you too.