Gigabit connection between Cisco 2960 and HP 2510G

I am unable to set up a gigabit link between a Cisco 2960G-48 and a HP 2510G-48. I currently do not need trunking (tagging), but I have tried setting it up with and without it. I have a separate link between the same HP switch and a Cisco 2960-24 that has worked perfectly for years. The speed/duplex settings are auto on the Cisco switch and auto-1000 on the HP (the HP does not have a 1000 configuration - only auto-1000). I have also tried configuring the Cisco at 1000/full. The link that works does not include the native vlan on the Cisco switch, but otherwise the configuration should be the same. I have configured the 48-port Cisco exactly like the corresponding port on the 24-port Cisco except the vlan settings, but it does not work. Both switches show 1000 Mb/full duplex connectivity, but I cannot get any information to pass between them. If I configure both for 100/full duplex, then they communicate without problems. The only thing I have not done is rebooted both switches since it is hard to find a window to do so.

Thanks in advance for your help.