We do not support generated transactions from pools like Eligius, P2Pool etc.
What does this mean technical?
It means technically they don't support generated transactions from Eligius or P2Pool.

what is the difference between to receive NMC on a Namecoin client with a NMC address and to receive NMC in BTC-E with a NMC address?
that was my question. how can you prevent to receive NMC on a Namecoin address technical.
Eligius and P2Pool pay you with "generation" type transactions. These can be orphaned, and also can't be spent for 120 confirmations. BTC-e's system for processing deposits will not properly recognize a generation type transaction.
BTC Guild's payments are all sent using standard address-to-address type payments.