[c-nsp] weird issue with IBM blade cente switch 3012

[Alex Wa]

Hi guys,
 
I have to configure several Cisco 3012 switches for a project and i'm kind of stuck with an issue I can't really figure out. 
 
This is the situation. I have a two 6509s core to which i'm connecting 12 3012s. most of them work fine but with 3 of them i'm not able to ping each other (through 2 vlan interfaces on same vlan). trunks are configured between them, spanning tree runnign as it should, vlan allowed on trunk, I even see each other through CDP.  let's say 6509 side is A and 3012 is B.
 
 situation #1: when you ping B from A, B have correct entries in the arp and mac-add tables (for A), A doesn't have them for B. A still unable to ping B
 
situation #2 when you ping A from B, B is not able to resolve A's mac-add so arp entry for A is incomplete. but the curious thing is that even when B has A mac-add  (situation A) it's not able to ping A.
 
debug commands show encapsulation failure (as it should with an regular incomplete entry). nothing on the log. masks verified as the same.
 
Also tried creating all over again with different secuence (VLAN, int VLAN, trunk) with same results. And, the most weird thing of all: it works on some switches with the exact same config and layout!!
 
comments, sugestions, ideas on what to do next? any help will be highly appreciatted
 
alejandro wainshtok