[G4] Kingston 512 Ram Memory Dilemma

[Harold Polk]

I recently added another "stick" of Kingston 512MB of memory in my G4  
MDD, to add to the Samsung 512MB stick installed by MacZone at  
purchase and another Kingston 512MB that I had added about a year or  
so ago.  I have been having trouble with the internal modem not being  
reliably activated by the system and thought it might be a memory  
problem.
I ran the "Apple Macintosh Hardware Test" disc that came with the  
computer and this test tells me that the newest stick is defective.   
However, when I run TechTool Pro 4.04 all the sticks show good.  Now  
which test should I believe, the Apple program or TechTool???
I am aware that the Mac's are sensitive to memory but why would one  
test show defective and another test show the stick good.  BTW I did  
change the slot of the "defective" stick and it again showed  
defective using the "Hardware Test" but TT shows it good.  Have not  
talked to Kingston but this is my first option.
Any ideas on this dilemma would be greatly appreciated.
Harold