When I installed BOINC - on a Vista PC :(
boinc.exe is running ok, but the manager can't attach to the client - eg. I can't attach to a project, when I try I get this message :

BOINC Manager is not currently connected to a BOINC client

Selecting localhost as the attached computer, and using the default password/deleting/copying the content of gui_rpc_auth.cfg into the password field makes no difference.

I've installed both as administrator & normal user, and with single-user & multi-user options.

Make sure you allow BOINC through your firewall for localhost. BOINC's parts communicate on port 31416, so you must set boinc.exe and boincmgr.exe as allowed through the firewall.

Also, don't install BOINC in the default directory. See this FAQ on that.

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Thank you for your lightning fast response.
Problem solved. I have the excellent Eset Security Suite, with quite restrictive firewall settings.
Things are working now I've added rules to allow boinc.exe to access ports 31416 I also added port 80, so it could access projects.
Following your advice I'll move it to another directory

I also added port 80, so it could access projects.

If you want to work on World Community Grid (and a couple others, but of WCG I know it) you also need port 443, secure HTTP.

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