I discovered that all information about links to my site disappeared from Google Webmaster Tools. Last time I checked the Links to your site page in GWT there was nice list of linking domains and all. But now there is only No data available. There were no changes to the site contents.Why could it be? And what can I do to fix this?About a month earlier I found that PR of all my pages dropped by 2 points. May these changes be related? 
Information about links disappeared from Webmaster Tools
pagerank;google search console;backlinks
This happened to me recently too. I am not sure why it happened although it might be related to that Google change the happened recently. I didn't do anything to cause it nor to fix it. I waited a week and all of my data came back. It also might be that Google is in the middle of reindexing your site. But that is speculation. But if I were you, just wait a bit and see if it comes back. If it is like mine was it will in about a week. My rankings didn't change during this time, so I don't think Google actually lost all my data. 