Hi I am one of the experts here on Just Answer.com
I have a question if you press and hold the shift key while clicking on more than one line are you able to select multiple objects?
Sorry I had to step out of the chat so I switched the question to Q&A format
one thing to check to make sure you havent changed a setting is to
check options, selection, and make sure "use shift to add to selection" is not checked
Preference can be altered by many different key combinations
Did you check options go to selection and make sure "use shift to add to selection" is not checked?
If this is checked than you will not be able to select multiple items without the shift key
Should be in your options under tools
If its not there in the command window try this
when it asks you for a value type in 1 and hit enter and see if that works
once you enter 1 and hit enter try selecting multiple lines
that value of 1 turns on the multiple selection
So is everything now working the way you wanted it to?