If the game was humming along fine and then suddenly a problem like this occurs, it is almost always due to custom content either incompatible with your EPs/SPs or else in conflict with some other custom content.
Did you recently install any hacks?
Did you recently install any hacked objects?
Did you recently install any new lots?
Any of those could be how something creating the problem was added to you Downloads folder.
Would suggest running Clean Installer (which highlights hacks in red) and looking for phone-related hacks, then temporarily moving those from Downloads and checking if the problem then goes away.
You might also want to run Paladin's Hack Conflict Detection Utility to see a listing of potential conflicts.
Clean Installer:
http://sims2pack.modthesims2.com/index.php?page=3Paladin's HCDU (click Sims 2--Programs there):
http://simwardrobe.com.