We were having the same issues and had 12 networked HP3600 printers. Finally decided to replace them as needed and would you know we replaced 4 and then found a soluton with the drivers and Windows 7 64 bit. Completely uninstalled the existing 3600 driver and then installedthen using the CLJ_3600_Beta_winxp_vista_X64 driver.
so far no issues. We had to use this driver on 5 Win7 systems so far and they all took it just fine.
below is the link to the driver. Hope this helps some of you.
ftp://ftp.hp.com/pub/softlib/software11/COL31397/ly-77954-1/CLJ_3600_Beta_winxp_vista_x64.zip
