Hi,

Yes check the cables & connections first. Maybe even different cables should you have some to use. Also check to see if this occurs on all the guitar models or if it is a specific one.

If you get the squeal at all times no matter what, try reinstalling the guitar's flash memory in Line 6 Monkey. You will need either a Variax Workbench interface, a POD xt/X3 or a Vetta amp to do this.

If not, you will need to take this to an authorized service center found here: http://line6.com/support/serviceCenters/. You have a 1-yr parts & labor warranty so long as you purchased it new from an authorized dealer & have your receipt.

Thanks

Line6Sach

Glad to hear it was resolved!