The following problem:

I need to write interface name into zabbix_agentd.conf, since its name is always different, like so:

PerfCounter=uNetwork.all0,"??????? ???????(Realtek RTL8139 Family PCI Fast Ethernet NIC)??? ??/?",60

I have been doing this for a year using script with success, but in 1.8 agent here what is happening:

1) PerfCounter=uNetwork.all0,"??????? ???????(Realtek RTL8139 Family PCI Fast Ethernet NIC)??? ??/?",60

zabbix_agentd.log LOG: (unreadeable symbols must be UTF-8 since log in windows is in ANSI)
19468:20091218:153607.241 cfg: para: [PerfCounter] val [uNetwork.all0,"\??????? ?????????(Realtek RTL8139 Family PCI Fast Ethernet NIC)\????? ????/???",60]
19468:20091218:153607.241 Accepted configuration parameter: 'PerfCounter' = 'uNetwork.all0,"??????? ???????(Realtek RTL8139 Family PCI Fast Ethernet NIC)??? ??/?",60'
19468:20091218:153607.241 In add_perf_counter() [counter:\??????? ?????????(Realtek RTL8139 Family PCI Fast Ethernet NIC)\????? ????/???] [interval:60]
19468:20091218:153607.241 Unable to add performance counter '??????? ???????(Realtek RTL8139 Family PCI Fast Ethernet NIC)??? ??/?' to query: ???°?- ?°?‹?µ ???±?µ?‚?‹ ???µ ???°?µ?‹ ?? ?????‚?µ?µ.
19468:20091218:153607.241 Alias added. [uNetwork.all0] -> [__UserPerfCounter[uNetwork.all0]]
....
19648:20091218:153607.288 In add_check('uNetwork.all0', 300, 0, 0)
.....
19648:20091218:153619.147 For key [uNetwork.all0] received value [?????°?- ?°?????‹?µ ???±???µ???‚?‹ ???µ ???°?????µ???‹ ?? ???????‚?µ???µ.]
19648:20091218:153619.147 In process_value('agentname','uNetwork.all0','???°?- ?°?‹?µ ???±?µ?‚?‹ ???µ ???°?µ?‹ ?? ?????‚?µ?µ.')

That's all after that it switches to NOT_SUPPORTED in Frontend

AT THE SAME TIME zabbix_get is working:
#zabbix_get -s agentname -k perf_counter["\??????? ?????????(Realtek RTL8139 Family PCI Fast Ethernet NIC)\????? ????/???"]
66.064190

AND IF I create another completely independent item in Frontend, like so:
key=perf_counter["\??????? ?????????(Realtek RTL8139 Family PCI Fast Ethernet NIC)\????? ????/???"]
then this would work as well! However, I would be receiving thie error all the time, when I visist 'Latest Data' page:

Incorrect usage of quotes. ["\??????? ?????????(Realtek RTL8139 Family PCI Fast Ethernet NIC)\????? ????/???"]

2) Also completely differnt userparameter:

PerfCounter=uCPU,"?????????(0)% ????????????? ??????????",60

when added, prevents zabbix agentd from starting:
agentd LOG:
17628:20091218:155721.584 cfg: para: [PerfCounter] val [uCPU,"\?????????(0)\% ????????????? ??????????",60]
17628:20091218:155721.584 Accepted configuration parameter: 'PerfCounter' = 'uCPU,"?????????(0)% ????????????? ??????????",60'
17628:20091218:155721.584 In GetCounterName() pdhIndex:0
17628:20091218:155721.599 Can't make counter path: ?????????‰?µ ?» ?µ?µ?µ ?±?- ?°?‚?µ?»???‹ ?°???????µ?‚.
17628:20091218:155721.615 PerfCounter "uCPU,"?????????(0)% ????????????? ??????????",60" FAILED: Invalid format.