Is it a multisync monitor? You perhaps need to configure the monitor's settings on the monitor. When using the GUI the frequencies of my monitor are 81.9KHz/89.9Hz, if I switch to tty2 the frequencies are 48.3KHz/59.9Hz on an Arch Linux install using the radeon driver. My multisync monitor remembers different settings for different frequencies.
I am not sure how to tell if I have a multisync monitor. My monitor's menu does not offer a way to adjust the size of the screen area. I can tell you that in X, I am seeing a frequency of 67.5khz / 60hz np, and on tty2 I see the same frequency. Pressing the "auto" button results in a popup on the monitor that says "Auto adjustment: Not available".
-- Love, Mike Bailey