QUOTE (psfred @ Sep 2 2008, 12:43 PM)

I'm not familiar with the Sonnet, but it could be a leaking converter or cartridge nipple -- this will allow ink to seep out the threads that hold the barrel on.
Rinse out and dry the cap, wipe the pen off well, then try to determine exactly where the ink is showing up. If the nib is flooding and the cap fills with ink, you have a leak in the conveter or a leaking cartridge. This will allow ink to simply drip out of the pen. It will also flood ink while writing if this is the case. If it leaks at the barrel threads, the nipple is leaking ink.
Or it may be cracked somwhere in the section, allowing ink to seep out.
As noted, shaking the pen with the cap on and point down will fill the cap with ink, I don't know of any FP that will tolerate much vibration nib down without dumping ink. This includes fast walking, riding a bike, or any vigorous activity with the pen in a pocket or backpack.
Peter
I have a vintage lever filler that is doing exactly that. Does this mean I need to resac it?