Imac crashing/flashing when performing tasks

Question

Hi Guys,
My Imac (Late 2011 21.5 Inch) is show casing a few odd issues the past week that are a bit scattered, I can't really connect them to one common diagnoses. Maybe you guys can shed some light on it for me please??
1. Start up is suddenly taking longer than normal.
2. Today, when performing an Iphoto Data transfer to USB it kept failing. The screen briefly flashes and the task is no longer viewable on the monitor. It was only possible to complete if I lowered the data transfer. I had 430 pics to transfer. I had to do it in chunks of 25 in order to complete the transfer, other wise it would Flash quickly and the task would fail.
3. I use Logic Studio mostly on my Imac. If you are familiar with this soft ware you'll know about Plug Ins and the channel where they are viewable. This week the Plug Ins all had black lines through them as if they couldn't be located? This made me cry like Id lost a parent suddenly. Im still grieving 
Finally.
4. The main menu bar at the top of the screen doesn't appear, unless you click on any given App etc. I click finder to make it appear or Itunes etc.
Clearly there is an issue but from the above, but do these symptoms collectively shout out an obvious diagnoses to you guys?? I get the feeling Il have more examples pretty soon  Additionally, Am I right in thinking there is a diagnostics test on-board I can run to determine any detectable errors??
Appreciate any input!
Thanks 

Answer 1

When you have the problem, note the exact time: hour, minute, second.  
These instructions must be carried out as an administrator. If you have only one user account, you are the administrator.
Launch the Console application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad and start typing the name.
The title of the Console window should be All Messages. If it isn't, select
          SYSTEM LOG QUERIES ▹ All Messages
from the log list on the left. If you don't see that list, select
          View ▹ Show Log List
from the menu bar at the top of the screen.
Each message in the log begins with the date and time when it was entered. Scroll back to the time you noted above.
Select the messages entered from then until the end of the episode, or until they start to repeat, whichever comes first.
Copy the messages to the Clipboard by pressing the key combination command-C. Paste into a reply to this message by pressing command-V.
The log contains a vast amount of information, almost all of it useless for solving any particular problem. When posting a log extract, be selective. A few dozen lines are almost always more than enough.
Please don't indiscriminately dump thousands of lines from the log into this discussion.
Please don't post screenshots of log messages—post the text.
Some private information, such as your name, may appear in the log. Anonymize before posting.