Any notes (as well as files) you save can be quickly accessed from the item itself in the center column. Just toggle the arrow to the left of the item to reveal any attached notes or files.
The most important tip I can offer about troubleshooting is to have you read Zotero's instructions on backing up your data. No matter what issues you mau run into with your data, if you understand how to create a backup, all will be well.
Additionally, Zotero offers a nice checklist of troubleshooting tips to try when all else fails: https://www.zotero.org/support/troubleshooting_translator_issues. Also, you can report your troubles to Zotero:
First, locate which version of Zotero are you using. To locate this, click on the Help menu and choose “About Zotero”
Next, Try to add a new citation to Zotero or try to do whatever it is that's causing the problem. Right after you do this and the citation disappears, Select the Help menu and choose
The window should include information about the problem, click next and submit the information to Zotero. The resulting window will provide you with a reporting code/number. Register at Zotero Forums and log your issue.
It seems like a great idea to check the box to "enable proxy redirection," but it's really not. Especially if you do research at several universities, this option can cause problems and general proxy confusion. Zotero may also attempt to proxy resources (like WorldCat), that should never be proxied. Proxy preferences are now located in the Zotero browser connectors. Just right-click to display your options:
and uncheck the "Enable proxy redirection" setting: