Since both the Dell site and the crucial memory site list a 1GB max per slot, I suggest that you run a full set of memory test like Memtest.
Dell an Crucial said it doesn't make it a fact. Sorry, but that is the truth. Dell just posted what they tested the system with, Crucial just parrots what Dell tells them is compatible. Dell and Crucial also stated the same for the Inspiron 1501 and I have been running my Inspiron 1501 with 4GB for well over a year. ( 2GB in each slot ) for over a year and it passes Memtest ( 24 hour run ) and Windows Vista memory test ( 24 hour run ).
Note you have to be careful what memory type you install as notebooks can be finicky about the type used. I do agree about running a memory test for an extended time period to ensure that it is working as designed. The chipset type will tell you how much ram it should support.