I did uninstall and then tried download and install 7.8.3
Same result, Boinc.exe lanches and quits. Manager then can't do anything.

Can't add any project (list is populated, but each project answer "unavailable" prior to password request)

This is boinc without vbox

This is single user

Somehow I managed once to add ibercivis project but that is not the one i want now.

first lines of log:

10/27/2017 2:34:46 PM | | cc_config.xml not found - using defaults
10/27/2017 2:34:46 PM | | Starting BOINC client version 7.8.3 for windows_x86_64
10/27/2017 2:34:46 PM | | log flags: file_xfer, sched_ops, task
10/27/2017 2:34:46 PM | | Libraries: libcurl/7.47.1 OpenSSL/1.0.2g zlib/1.2.8
10/27/2017 2:34:46 PM | | Data directory: C:\ProgramData\BOINC
10/27/2017 2:34:46 PM | | Running under account admin
10/27/2017 2:34:46 PM | | OpenCL: Intel GPU 0: Intel(R) HD Graphics 505 (driver version 21.20.16.4534, device version OpenCL 1.2, 3202MB, 3202MB available, 108 GFLOPS peak)
10/27/2017 2:34:46 PM | | OpenCL CPU: Intel(R) Pentium(R) CPU N4200 @ 1.10GHz (OpenCL driver vendor: Intel(R) Corporation, driver version 6.6.0.359, device version OpenCL 1.2 (Build 359))
10/27/2017 2:34:46 PM | | Host name: VOYO-MINI-COMPTA
10/27/2017 2:34:46 PM | | Processor: 4 GenuineIntel Intel(R) Pentium(R) CPU N4200 @ 1.10GHz [Family 6 Model 92 Stepping 9]
10/27/2017 2:34:46 PM | | Processor features: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss htt tm pni ssse3 cx16 sse4_1 sse4_2 movebe popcnt aes rdrandsyscall nx lm vmx tm2 pbe fsgsbase smep
10/27/2017 2:34:46 PM | | OS: Microsoft Windows 10: Core x64 Edition, (10.00.15063.00)
10/27/2017 2:34:46 PM | | Memory: 7.84 GB physical, 9.09 GB virtual
10/27/2017 2:34:46 PM | | Disk: 117.72 GB total, 90.59 GB free
10/27/2017 2:34:46 PM | | Local time is UTC +2 hours
10/27/2017 2:34:46 PM | | VirtualBox version: 5.1.26
10/27/2017 2:34:46 PM | ibercivis | URL http://registro.ibercivis.es/; Computer ID 470218; resource share 66
10/27/2017 2:34:46 PM | | General prefs: from http://asteroidsathome.net/boinc/ (last modified 29-Apr-2017 10:12:22)
10/27/2017 2:34:46 PM | | Host location: none
10/27/2017 2:34:46 PM | | General prefs: using your defaults
10/27/2017 2:34:46 PM | | Reading preferences override file
10/27/2017 2:34:46 PM | | Preferences:
10/27/2017 2:34:46 PM | | max memory usage when active: 4012.45 MB
10/27/2017 2:34:46 PM | | max memory usage when idle: 7222.41 MB
10/27/2017 2:34:46 PM | | max disk usage: 82.59 GB
10/27/2017 2:34:46 PM | | don't use GPU while active
10/27/2017 2:34:46 PM | | suspend work if non-BOINC CPU load exceeds 25%
10/27/2017 2:34:46 PM | | (to change preferences, visit a project web site or select Preferences in the Manager)
10/27/2017 2:34:46 PM | ibercivis | Sending scheduler request: To fetch work.
10/27/2017 2:34:46 PM | ibercivis | Requesting new tasks for CPU and Intel GPU
10/27/2017 2:34:48 PM | ibercivis | Scheduler request completed: got 0 new tasks
10/27/2017 2:34:48 PM | ibercivis | No tasks sent
10/27/2017 2:34:48 PM | ibercivis | Project has no tasks available

then log grays out, and manager is trying to connect to localhost ...

If i try to add a project when manager is connected (lasts several seconds)

then the answer is "project temporarily unavailable"