"installation already running" error

i have just got a iphone, and to get it to wrk i have to upgrade my itunes/quicktime and safari to the latest versions. but when i click to update i get errors coming up saying its already running somewhere else and i have to close it down to continue with the current install but i can t see anywhere where this is running. on the itunes update screen i get a little red error icon nxt to each of the updates and at the end says i have to manually download it but again i get the same error message........ im tearing my hair out over this.it must be a simple fix that im not seeing as i can install other programs fine. please has anyone had this problem and found a solution?