update of the virus signature database not necessary

I've ESET NOD32 Antivirus Business Edition on 40 computer(s) valid until 05/26/2009
but since 1 month ago all computers stop updating in the first branch then since 2 days the main Branch stop also updating too, even so every thing seem to be ok, and when I try to update, the nod32 says "update of the virus signature database not necessary"
Kindly, help.

 

are they updating a) from mirror or b)from eset servers?

a) delete contents of mirror folder on server, run update now in console
b) try to clear cache

 

thanx, i already did both actions and nothing happened

 

where are you updating your clients from then? mirror or eset servers?

check your log file

 

OK, my antivirus structure divided into:
1- Two local servers pull updates from the internet "eset servers" for both 2.7 for exchange server, and 3.0 business versions and both are deploying the update through two mirrors in each branch
2- All laptops take the update from the internet "eset servers" directly
Totally are 37 machines and no Server, PC or laptop able to update now