we have some trouble with copper sfp's in a 7604 with sip-400 and SPA-5X1GE-V2 or 7600-ES20.
We tried some other sfp's but the link on the 7604 is still down. We don't have the problem with fiber sfp's.
Negotiation cannot be configured on the interface,
You need SFP-GE-T, according to the release notes, I don't see GLC-T listed for support under SPA-5X1-GE-V2