[Serusers] Radius Auth : 407 proxy auth and Get-User-Attr - crash

Hello all, i'm using SER 2.0 with Radius accounting and authentication - based on x64 ubuntu machine. i've a problem with the Radius auth, and only for the proxy auth mechanism (method INVITE) : depending of the topology of the UAC, it crashes the SER or a there's a 407 proxy auh required. when the UAC is behind a simple NAT, i get the 407, with "preauth: credentials with realm 'sip.720.fr' not found" - i tried many configs, no way it doesn't work. but the REGISTER is ok - it's the same Radius request ? when the UAC is behind NAT but in a VPN (our customers), proxy auth is successfull even if the preauth don't find the credentials with the realm (why? it does not differ from another uac without VPN ???), but when SER requests the Radius to get the user attributes, it crashes ! in each case, there's no pbm with REGISTER requests. Radius user sample : 1010(a)sip.720.fr User-Password = "pwd" User-Name = "1010", SER-UID = "1010(a)sip.720.fr"0.fr", SER-DID = "1", SER-Digest-Username = "1010", SER-Digest-Realm = "sip.720.fr", SER-Uri-User = "1010(a)sip.720.fr" Does anyone have any idea, or met already this problem ? What I have to verify ? Thanks for help, Samuel MULLER