I seem to be getting the same issue. Even more interestingly, when I remove that digital clock widget, Dashboard seems to always freeze. It would seem likely that Big Digital Clock is the culprit here. It must be running in some sort of loop that not only makes its RAM usage balloon, but prevents Dashboard from closing it, and causes it to freeze.
This is after only a few minutes. Then I tried to remove Big Digital Clock, and Dashboard has been "Not Responding" ever since, although its RAM usage keeps climbing. Although this doesn't happen immediately. It would seem that the clock needs to be running for a few minutes before it exhibits this bug.
EDIT: It would seem the steps to trigger this bug are as follows (there may be a step or two in here not necessary, but this does it). Do this after removing all widgets to start fresh:
- Add Big Digital Clock
- Add calculator
- Do 2 + 2 (or some arbitrary calculation that you can hold down the enter key for awhile with) and hold down Enter for like 20 seconds
- Delete Calculator
- Add Calculator
After these steps are completed, Dashboard should start to bloat in a few minutes. You'll know you've done it right if you start seeing small CPU usage spikes with Dashboard every 15 seconds (this may be related to the 20 seconds or so of holding down return in calculator). After Dashboard bloats to about 1 GB of RAM, trying to get rid of Big Digital Clock, results in Dashboard going unresponsive.
The solution seems to be to remove Big Digital Clock, as it seems to be the source of this systematic bloat. Let me know if this experiment works for anyone else.