Pop/Clicking sound when I start and stop!

[chromeboy]

Hi everyone, I need some help with a problems that driving me crazy...Everytime I press play and stop of pro-tools, i get a tick sound. When i'm not working with effect tick sound is not very annoying but when put a Delay or a reverb..WATCH OUT! lol...Now , what is really strange for me is that i get this problems with my pesonal computer at home XP Pro, Quad Core, 4 Gb Ram 1.5 TB HD and with my computer at work Mac Pro 2x Xeon Quand Core ,2GB,500 GB HD...Im running PT8 LE (mBox 2) on both computer with the latest update. I also try all the different setting in the playback engine nothing seems to work...

Thanks for your help

[chromeboy]

and i forgot to tell that im not running big session...sometime its only 1 guitar track or 2 or 3 voice over with 2 or 3 eqs

thx again

[spkguitar]

Does it happen at all in a session with no audio in it?

[chromeboy]

No, it does not happen with no audio track...I also recorded a room tone and everything is alright when I press play and stop...