The affected users - there are 80 pages of people discussing the issue on the forum - have discovered that in addition to running Windows 7, they are all using computers with the Intel P55 Express Chipset.
Intel is investigating the issue and believes it is a BIOS or system configuration issue, but the company is still investigating, an Intel spokesman said.
On Sunday, an Apple employee posted a note on the forum asking people with Windows 7 PCs that have the Intel P55 chipset to email the company with specific details about their computer, iPhone model and the behaviour they're seeing. The note indicates that Apple is also investigating the problem.
Microsoft said it hadn't seen questions about the problem on its Windows 7 help forum or received calls about it. However, it has reviewed the discussion on the Apple forum and is investigating, it said. If it finds the issue is related to Windows 7 it will post a note on the Microsoft Answers help site.
Some people on the Apple forum say they've had some luck reverting to an older version of iTunes or even switching to Windows XP mode on their computers.
The Register reported the problem on Friday.