External monitors issues...

[chait]

I have an x60s with an Ultrabase. The x60s may be connected one time directly to a 1280x1024 external screen, or to a wide screen (1680x1050) via the Ultrabase. If it first connected to the 1280x1024 screen and eventually the x60s is turned off, then when I place the x60s in the Ultrabase, it is unable to set the external screen resolution to 1680x1050 (I have to change graphics properties each time to this resolution). I hope my question is clear enough, though I am surely revealing my level of ignorance. Thanks in advance.