Windows Vista is in more legal hot water and this time the ones getting wet are the companies who've rolled out the operating system, not Microsoft.

A series of lawsuits have been brought against major US companies by staff claiming unpaid overtime based on the time it takes Windows Vista to start up and shut down.

Mark Thierman, a solo legal practitioner based in Reno, Nevada, told The Reg employees are losing up to two hours of pay a week thanks to Windows Vista.

Thierman calculated damages could run into millions of dollars over a three-year period. He's representing employees of Cigna health insurance, with cases also pending against AT&T Inc and UnitedHealth Group covering thousands of employees.

Thierman said the Windows Vista problem particularly affects workers paid by the hour, in places like call centers or in retail.

The crux of the issue is the fact that some companies have connected time-keeping systems to their PCs.

These systems are not activated until the user logs in, which is taking up to 15 minutes after the machine running Windows Vista has been turned on thanks to the long boot cycle. This means staff are in the office or shop but not officially working until they've logged in

And when it comes to shutting down, people are logging off but hanging about without pay as the PC goes through the equally long shut-down cycle.

Thierman called the idea of wiring time-keeping systems into the PC a glitch that sounded like a good idea at the time. ®