How to update ESET SS BE via GPO without admin rights?

Hello everyone,

Does anybody has experience in upgrading hundreds of ESET Smart Security Business Edition with firewall turned on? When I'm upgrading any station from v4.0.474 to v4.2.40.10 the user experiences network disconnect for short moment (upgrading firewall components I guess). We have several services on network shares and I cannot afford to disconnect from network hunderds of people for a while.
Another problem is that users do not have administrator rights.
I tried to give users the possibility to self-installation with GPO ( http://kb.eset.com/esetkb/index?page=content&id=SOLN2185&actp=LIST ) . This works when ESET SS is installed on PC without earlier version of ESET (i.e. 4.0.x). but when ESET is existing I get a pop-up with "The Installer has insufficient privilidges to modify this file: c:\program files\ESET\ESET Smart Security\PPESET.dll" and several other files. ESET's support said me "Most probably it happened that there is still part of the previous self defense module active there which interfer with new installation and doesn´t allow it to finish correctly."
I still can not find a method of trouble-free ESET's upgrade.
Can somebody suggest something?