Problem accessing a Windows XP share from a Windows 7 PC

Today a problem drove me crazy: I tried to map a share on a PC running Windows XP from another computer running Windows 7. I kept getting the error that the username or password are invalid. On the other hand, accessing a share on the Windows 7 PC from the Windows XP PC worked fine. I could also use Remote Desktop on the Windows 7 PC to access the Windows XP PC so I know the credentials were fine.

It turned out that the cause for this was the system time of these two computers being off by more than an hour. Adjusting the time solved the problem for me.