Charts won't display correctly

[Daniel Smith]

I'm having trouble with charts in reports, such as "Expense  
Barchart".  When displayed, they are jumbled and unreadable.  They  
look like they were "printed" by a printer that is almost out of  
ink.  Text and lines, if they show up at all, appear as bits of  
magenta and cyan that aren't quite on top of each other; solid fills  
are pale or white.  It's very strange, and not something I've ever  
seen before.

Apparently something about my configuration is messed up.  I seem to  
recall generating "Expenses vs. Day of Week" weeks ago and getting  
the expected, readable output, so something is different now  
(although that may just be the GNUCash version...)

Is this something others have seen or know how to fix?

GNUCash 2.1.5 (also observed in a custom 2.2.0 build)
Mac OS X 10.4.10
Installed via MacPorts

—Dan