So, computer A runs Windows 7 Ultimate, computer B runs Windows 7 Home Premium. both 64-bit. On computer A I can map a drive to computer B. The other way around doesn't work--I get "the specified network password is not correct", even though it is correct. I've looked around and have tried a lot of potential fixes--reboots, running Windows update, enabling the guest account, changed various security policy settings, turned UAC off, enabling/disabling Homegroup, etc etc... Also right before the "specified network password" dialog comes up there a very brief one about "looking for credential tiles". It disappears immediately and goes right to the bad password dialog. These are home computers, no domain involved. This started happening out of nowhere, far as I can tell...no updates, no new software, no changes, nothing like that. Had been working fine for almost two years. Anyone have an idea of what I could try next?

Hi, Click start-->run--> rundll32.exe keymgr.dll, KRShowKeyMgr, please delete all the saved credentials for a test. if the issue still occurs, please enable the policy Permit guest logon computer b via Network in secpol.msc. Also, you may disable the password protected sharing in Network Sharing Center. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Thanks for replying. I ran the rundll32.exe command on both computers, still the same problem. Password protected sharing was already disabled on both systems. Can you explain a bit more where to find "Permit guest logon computer b via Network in secpol.msc." Not sure where that is...I found the Local Security Policy tool, just don't know where that setting is. Thanks again

Well I'm very confused now, the problem has flipped. I rebooted computer A into a previous operating system--Vista, which also had a different computer name--and found that computer B _could_ connect to it. So I rebooted back into Windows 7 on A, changed the computer name, rebooted, and found that B could now connect to A. But now--of course--A cannot connect to B. Same error messages and everything. Tried renaming B, which didn't help.