clock/calendar location on screen

I have the time and date applet on my task bar ("toppanel", though i put mine on the bottom, Mac-style). When I click on it the calendar pops up and when I click on it again the calendar goes away. So far so good, but lately instead of popping up directly above the applet it pops up higher and higher on the screen, often blocking what I need to look at. At one point it actually came up off the top of the screen. I removed the clock from the panel then added it back, that brought it down to a more reasonable altitude, but it's still way up in the middle of the screen. Shouldn't I be able to move it around, or at least get it to come up down in the corner like it used to?