Wireless connections for internet when used for high bandwidth use programs are not reliable. Use ethernet cable if you can, that will probably solve your problem.

Other than that, go to LW's menu bar, Tools -> Options -> Advanced -> Transfers, & check the options for both upload & download Limit your bandwidth & a slider will appear. You can adjust these down so not too much bandwidth is being used for either.

LW 5 is supposed to limit bandwidth so it does not affect other internet use. However, looks like it does not take into account wireless systems where there might be some unreliability in bandwidth which is a typical behaviour of wireless internet.

You might also look into possible upgrades of the firmware your router uses. It's worth checking to see if there are any firmware upgrades available for your router. It might help in regards to the side-effects like you are suffering.

Wireless systems when used in high bandwidth situations are reknown for unreliability; drops in bandwidth, inconsistent bandwith, & at worst even the router losing connection. Depends on brand & model as to how bad this can be.

Edit: Sharing torrents is a typical issue with wireless systems not being able to cope. The high number of connections to & from that torrents create are often part of the cause, not only the bandwidth.