Oops: Nebraska ETV Network VS NBC...
NBC went through a logo rebranding in 1975 only to be sued soon after by Nebraska ETV Network for trademark infringement. The two logos were virtually identical using two inverted trapezoid shapes to create a stylized "N" icon. ETV paid only $100 for the design of their logo while the NBC logo redesign broke the bank at over $600,000.
The two networks came to an out of court settlement worth over $1 million. NBC got to keep all rights to their nifty new logo in exchange for giving ETV a color mobile unit and other equipment worth over $800,000. NBC also paid an additional $55,000 for ETV's legal fees and rebranding.
Sources: mentalfloss.com, wordiq.com