[xmonad] Problem with manage hook

Hi, I use this manageHook: mh = ( ask >>= doF . sink ) It works well except for a single application ('netgen', which uses a widget set that I can't identify). When it opens a dialog window, everything starts to flash (like if black and white lights were alternating fast). My wild guess is that when my manageHook changes a widget parameter (size?) the widget reacts changing it back, and I get an infinite loop. Do you think I could improve my manageHook to solve that? Thanks for your comments, Maurício