Strange Characters in Ping Window

After hours of my computers being on I lose access to the internet on the PC that decides to stop working. Unfortunately I unable to attach a picture to show you but I will try to describe the best I can. The offending line looks like the following:

Pinging yahoo.com [oy] with 32 bytes of data:

The strange part is the: [oy]. The o is actually a degree symbol and teh y has two dots above it. Can someone tell me what is going on here?

Thanks,

Paul