same servers, same strings, different responses

[Technicalx]

tried posting earlier, but didn't seem to work.
we are not using insight manager.
we are using GetIF 2.3.1 and deleting the .index file with every new mib brought in.
we are also using other mib walkers and get the same results...some servers reply to specific OID strings, some don't.

Problem:
20 DL 380 Servers, same BIOS, same windows 2003
all patched.
using various MIB walkers with downloaded mibs from compaq website (hpd801mib).
run a snmp poll with oid .1.3.6.1.4.1.232.19.2.2.4.0 on all 20 servers, maybe 10 will reply with data. run other strings and the same 10 will reply with data.

why won't all servers reply to the same strings, when they are configured/patched the same?