I know what ur going through as i suffer the same.
the Virus infecting ur pc is called Avkiller.agent.c (might be .A, .B and so on...).
this virus targets HJT, AVG and other antivirus softwares. it of course goes along with other trojans that download themselves onto ur computer.
i'm trying to find a solution as well, i haven't recovered my pc yet.
u should try scanning ur pc with Bit defender and panda. thats a good start to identify the file name and location of the infection. then post the logs here or on HJT analysis forum.
i suspect u will find a file named HJThis101.dll on ur windows' system32 folder, as i did, plus some other trojans.
u can check out my post and the recommended solution they gave me on this link :http://www.bleepingcomputer.com/forums/t/87003/infected-by-trojan-downloaderwin32delfpa-trojanstwoyle-avkillerc-and-more/
u might not be able to open the link from ur computer, due to the virus, so i suggest u try of a diff pc.
hope it helps,