KB: Freezing or long delays

Solution Details

Try going to Preferences ► Data Management ► Servers ► expand the Known Servers item > then click the "Clear Cache" control at the lower right of that (the servers section) panel.

Try working in an offline mode which can be accomplished by roaming a license...
This document should help with roaming:
https://www.altium.com/documentation/knowledge-base/altium-designer/roam-check-out-a-license-for-offline-use

...then disconnecting network activity by going to Preferences ► System ► Network Activity ► then clearing the check box for Allowed Network Activities.  Here's documentation that may help:
https://www.altium.com/documentation/altium-designer/accessing-defining-managing-system-preferences#!network_activity
 

 
If the issue is thus resolved, a network traffic issue is confirmed.  If you already know that the internet connectivity is intermittent, working offline may be a good solution.  If your network connectivity is good, you will need to look into other causes.
 
You can try turning off the local firewall on your computer to see if that helps.  In some installations, when the client is started for the first time the local firewall will present check boxes to ask if x2.exe should be allowed to pass traffic to local trusted networks, domain networks, and public networks.  If these boxes were not checked, the local firewall may be blocking traffic.
 
The network you are using may be blocking traffic.  Try bringing your computer (if portable) to a different internet connection (try it at home) or (if WiFi enabled) disconnect from your network and connect to a cell phone that has been set up as a WiFi hotspot.  If you are connected to a VPN, try working with it turned off.  If your colleagues on the same network experience the same issue, it may be your organization's router/firewall that blocking traffic. 
 
These tests/indicators point to routers, firewalls, or VPNs being too restrictive. They may need to have some URL addresses/ports white listed to allow specific traffic.  Here is a Knowledge Base article that lists URL and port information that needs to be allowed:
https://www.altium.com/documentation/knowledge-base/url-address-and-port-information
 
You can try updating the driver for your network adapter from the manufacturer's web page, or switching to a different adapter, like between a hardwired connection and WiFi or using (or stop using) a docking station (for a laptop.)
 
You may need to get your network support team involved to see what traffic is being blocked.  You/they could try running a packet capture (sniffer) utility e.g. Progress Telerik Fiddler Web Debugger proxy, or Wireshark, to determine where the network traffic is failing (blocked connections.)

Check to see if you have SOLIDWORKS PCB Connector installed.  If you do, try uninstalling it.  Here's documentation about working with Extensions and Updates:
https://www.altium.com/documentation/altium-designer/extending-updating
 
Long delays when opening a project in Altium Designer can be related to unresponsive printer drivers. The first time a project is opened or saved Altium Designer polls all printers that are installed in the Windows Control Panel, if a response is not received from a printer, there can be lengthy timeout.  This issue usually only shows up for the first time of a new session and things work fine after that.  Uninstalling all printers can help to resolve the delay opening projects.  Reinstalling the printers one at a time and checking that projects open between each printer install can help to determine which printer is causing the delay.  Then you can try updating the print driver for that printer or leave it uninstalled.

Long delays can also be interpreted as slowness, so please also check these Knowledge Base articles:
https://www.altium.com/documentation/knowledge-base/altium-designer/general-slowness

https://www.altium.com/documentation/knowledge-base/altium-designer/slowness-at-startup

Long delays and "freezing" can also be caused by an out of date video adapter drivers.  Please see the section about your video board drivers, and the Video driver(s) note at the bottom in this Knowledge Base article:
https://www.altium.com/documentation/knowledge-base/altium-designer/when-things-don-t-display-or-print-properly

Removing your preferences is another easy thing to try that may resolve this issue.  The process is described in this Knowledge Base article: 
https://www.altium.com/documentation/knowledge-base/altium-designer/how-do-i-reset-the-altium-designer-configuration-to-the-installation-defaults