Apple is being sued over its screen rendering technology used in the iPhone and iPod Touch.
Meanwhile Microsoft faces accusations that it is using the unpopularity of the Vista operating system to make a profit from people who want to "downgrade" to the Windows XP operating system.
The Apple lawsuit has been filed in the U.S District for Delaware court and is being instigated by mobile phone software provider Picsel Technologies.
The company claims Apple has infringed its "rapid redraw" patent, which allows mobile phone users to navigate through on-screen content without experiencing prolonged screen update cycles.
Law firm Nixon Peabody LLP, which is representing Picsel in the case, said in a statement, "Without Piscel's technology, users can be subjected to prolonged delays while zooming and panning documents, web pages, and images. This core rendering feature is a key contributor to the unique visual experience delivered by Picsel."
Picsel ships its technology to some of the world's largest mobile providers, including Motorola, Nokia, Samsung and Sony Ericsson.
It said its technology has been included in more than 250 million devices worldwide.
Meanwhile a woman is filing a complaint against Microsoft for charging customers to downgrade to Windows XP when buying a computer pre-installed with Vista.
Emma Alvarado bought a computer from the Lenovo Group for personal use and had to pay US$59.25 to switch operating systems.
She intends to get compensation from Microsoft for herself and all those who have faced a similar situation.
According to documents filed at a Seattle court, she alleges that Microsoft has used its large market share to coerce OEMs and Internet access providers into agreeing to restrictive licensing terms for its Windows XP operating system, and then profiting from consumers wanting to downgrade.
"Consumers have encountered numerous problems using the Vista operating system, and these problems have been widely publicised in various media outlets, " said the complaint, as seen by the Seattle Times.
"Microsoft has used its market power to take advantage of consumer demand for the Windows XP operating system and to pay additional sums to downgrade to the Windows XP operating system," it added.
Alvarado's lawyers allege that to date, nearly one in three consumers purchasing a new computer has paid to downgrade the operating system from Vista to Windows XP.
