We quite possibly do have a vocab problem... sorry.
Here is a copy of the wireless debug log I sent to you privately. I definitely do not see the "run received broadcast" line you mention. It was set to default. I will try bypassing the firewall (although windows firewall should have told me it blocked something.) My antivirus (Avast) would also have told me it blocked something.
calibre Debug log
calibre 1.18 [64bit] isfrozen: True is64bit: True
Windows-7-6.1.7601-SP1 Windows ('64bit', 'WindowsPE')
('Windows', '7', '6.1.7601')
Python 2.7.5
Windows: ('7', '6.1.7601', 'SP1', 'Multiprocessor Free')
Starting up...
Started up in 44.35 seconds with 104 books
SMART_DEV ( 0.00: 0.004) _attach_to_port try ip address "" on port 9090
SMART_DEV ( 0.94: 0.804) startup_on_demand listening on port 9090
SMART_DEV ( 1.01: 0.002) _attach_to_port try ip address "" on port 54982
SMART_DEV ( 1.07: 0.000) startup_on_demand broadcast socket listening on port 54982
SMART_DEV ( 2.14: 1.010) run All IP addresses {'{5868ED74-6880-4DA6-A73A-18D2E12DD51E}': [{'broadcast': '192.168.1.255', 'netmask': '255.255.255.0', 'addr': '192.168.1.36'}], '{565C2226-9ACB-4A83-BE8E-FB963A7754B1}': [{'broadcast': '192.168.1.255', 'netmask': '255.255.255.0', 'addr': '192.168.1.141'}], '{4258F1B7-6D9C-449B-B8E9-A0CA4E551BC4}': [{'addr': '169.254.151.6'}], '{846EE342-7039-11DE-9D20-806E6F6E6963}': [{'broadcast': '127.255.255.255', 'netmask': '255.0.0.0', 'addr': '127.0.0.1'}], '{05D4E5F6-6342-4D5B-AC99-A82680C650AF}': [{'addr': '169.254.58.91'}]}
Update: content server works just fine now that I understand it. Downloads to CC, files are visible to me via CC, etc. I do note one difference- they download on the tablet to \sdcard\Calibre_Companion. When the wireless sync worked, they downloaded to \sdcard\Calibre_Companion\News.
Will report back in a bit when I try your wireless suggestion.
Update 2:
All solved. It seems unrelated to any potential bug in Calibre, or in CC. Before I booted into safe mode, I rebooted and ran windows startup repair...which found -and fixed- disk errors. It now connects wirelessly as it always did. Thanks for your help- at least now I know how to use the content server as well!
And to 'theducks' thanks for kicking in to help as well.
Cheers to all