It's possible that this is caused by a computer virus or other malicious file or program, so I would suggest that you run both an antivirus scan, as well as an antimalware scan, just to be sure that your computer isn't infected with anything.
If you need a free antivirus program, I would recommend that you try using Microsoft Security Essentials, which you can download from the link below.
As for a free antimalware program, I would suggest that you try using MalwareBytes, which can be downloaded from the link below.
If you are unable to download or run these programs because of this virus or malicious file or program, you may be able to do so by booting your computer into Safe Mode with Networking, where hopefully, you should be able to do so.
Also, I wouldn't suggest that you continue to use peer-to-peer filesharing programs, such as LimeWire or FrostWire, as downloading certain files is illegal and there is always the chance that you'll end up downloading a file that's infected with a computer virus or other malicious file or program.
Instead, perhaps you should purchase your files, such as music and TV shows, from an online retailer, such as iTunes or Amazon.
Good luck and I hope I helped you!