It's either an attack on your IT infrastructure, updates breaking something, or your IT doing some ~~suspicious~~ bold things.
Either way, create (if you didn't already) a *.BAT file on your desktop containing these lines:
net use * /delete
net use letterofmappeddrive: \\pathtothesharedplace /persistent:Yes
repeat the last line for each mapped drive and run the script every time something weird happens. You can also schedule it to run every an hour or so, until your IT provides a lasting solution to the problem.