Bl20pG2 hang after PXE boot

[Marais_3]

Hello,

I've got a problem with bl20p.
In fact, sometimes, when I need to reboot bl20, the server is stopping after pxe boot and it's waiting. I need to do it 5 or 6 times and then the os can boot correctly (win2003).
Signal backplane has been already changed.
the problem only happened in bay4, so I decided to swap between bay 4 and 7 (for exemple) in order to isolate the problem.
Now server in bay 7 does not have problem anymore and bl20 which was in bay 7 and now in bay 4 has the problem.So I'm wondering what could cause the problem...if someone has an idea it would be helpful !

Thanks,

Olivier