Strange Modem Connection Loss

[JamesMurphy]

Hello there people, i would like to see if some of you could shed some light on my recent strange re-occuring error i am now getting.....
Recentlly i Have been having this strange problem:
I have 2 Windows 2000 Computers both connected to my Linksys BEFSR41 Router, now When i have PC1 Connected to the router everything is fine. But when i connect PC2 to the router and use mIRC The modem light begins to flash and bails out and we lose our connection for quite some time On the Set Top Box. I say when i use mIRC becuase i have noticed it has only started to happen when i use this application all though there may not be a connection with the mIRC and STB failing i dont know, but if i have just PC1 on the router (and this computer doesnt use mIRC) the connection is fine. Any one able to shed some light on this?
Thanks very much.

[homealone]

presumably PC1 & PC2 work fine connected simultaneously, if you dont use mIRC?

What model of stb is it? - have you tried throttling back the upstream speed when mIRC is running?

Sorry it's more questions than answers ;)

[JamesMurphy]

No i havent tried limiting Upstream bandwidth but that cant be the problem as it never used to need limiting.
As we speak Im using both PC's PC1+2 Simultaneously fine without probs
But i havent used irc since i have gotten back online, just incase the modem does bail out again. :(