Microsoft confirmed that devices running its newest mobile software are unable to connect to a PC in some cases. The software maker said some users of ActiveSync 4, the latest version of Microsoft’s synchronization software, are unable to link up to their PC, particularly on systems running firewall or parental control software. The problem occurs in devices based on Microsoft’s Windows Mobile 5 operating system, including recently released handhelds from Dell and HP, as well as cell phones from Sprint and iMate.