[igraph] igraph crash on windows xp 64 bit system

[Gang Su]

Hi dear developers,

I have just migrated my working environment to a 64 bit system.
One weird issue i encountered is i tried to initialize a graph with 
around 5k edges.
However, R will crash if I load around 3k edges.
For example,
if I use graph(el[1:1000,]), it is fine
if I use graph(el[1:3000,]), R will crash

I am now using R 2.6.2 with igraph. I not sure whether this is a igraph 
bug or R bug for the 64 bit system. If you have used igraph on windows 
XP 64 bit system please help!
thank you very much!

Gang