There was a memory leak in the development version of Parcellite. Overlooking a single line of code is all it takes for your program to chomp at your memory like a hungry puppy. The following line fixes it:
Fix has been commited. Please update your working copies pulled from subversion and recompile. Also, I will be fixing some bugs with the Edit Clipboard window which has some weird behavior in different window managers. Soon after that another release will be made.