Root Issues upgrading to latest Froyo build

[robert_e_leet]

Brand new Android and Nexus One user here, I'm sure this is a very noob question but I've been looking for answers online for hours with no avail.

I just bought a rooted Nexus One with a FRF83 build preinstalled.
It's been working great but I keep getting messages about installing OTA updates but they always fail (says E: No signature (575 files) E: Verification Failed)
I tried manually downloading the FRF85 and FRF91 update, copying as update.zip to my SD updating from the recovery menu but it still gives the same error.
From the little info I've found online it may be an issue with the ROM but I can't tell for sure.
My ultimate goal would be to go back to stock Android with the latest official Froyo build.

Any help for this brand new and otherwise happy new Android/Nexus One user would be eternally apprechiated!

 

[bigfod]

Someone who knows more than me will be along soon, but if you're rooted you can't install the updates like that. I think you need to fiddle with your ROM.

 

[Rusty]

It's because you have a custom recovery.

If you want an OTA update then you replace the recovery with a stock one. If you just want to update to FRF91 then look on XDA Devs for a repacked update.zip that will work with custom recoveries.