Strange behaviour at startup

Hi,
I'm relatively new to Macs and so looking for some help to resolve my issue.
I have the following mac;
27-inch, Mid 2011Processor
2.7 GHz Intel Core i5
Memory 4 GB 1333 MHz DDR3
Graphics AMD Radeon HD 6770M 512 MB
Software Mac OS X Lion 10.7.3 (11D50b)

Over the last 2-3 week period when I boot up my mac from cold, it takes around 2 minutes to get to login screen and then once logged in the screen update speed is very slow.
If i go into launchpad and scroll between pages, the screen updates like a set of blinds upwards and is very unresponsive.
If I restart the mac then everything is fine but i don't understand why this is happening and it is really inconvenient to have to effective boot the mac twice each time i want to use it.

I have tried the Apple hardware check which has returned no problems and have also repaired all permissions in an attempt to fix, however the issue still persists.

Any advice would be greatly appreciated.

thanks

The next time you boot from a cold start, instead of rebooting, open your Activity Monitor app (Applications, Utilities, Activity Monitor.app) and look carefully to see if there is an unusual amount of activity going on. Look for heavy CPU and memory usage. If you find any, write down what's causing it and post back.

Hi chscag,
what sort of figures are we talking about when you refer to heavy CPU and memory usage ?

Two columns which are important:

%CPU

Real Memory

You can glance down both of those columns and get an idea of what you need to keep an eye out on. Percentage of CPU usages that are large (~50% or more), and heavy memory usage.

You can sort the columns by clicking the respective column titles. That should help in determining what might be causing you some problems.

Anything set up in Login items?

Ive just booted from cold again this morning to the same problem, the issue seems to be with applications.
When i click on launchpad it takes ages to appear and the screen continually refreshes itself from bottom to top in bars.

Once i eventually got into activity monitor there was nothing that stuck out other than something called kernal_task that was using 241.4mb of memory.
I then tried to open launchpad again with the monitor open which took ages again and spotted PEDcache using 100% cpu for a short period of time.

I repeated this a few times but couldn't get the PEDcache to show in the monitor again, despite the problem still presenting itself.

Any ideas ??

Try using disk utility to repair permissions on your HDD.

Mini_mi said:

Try using disk utility to repair permissions on your HDD.

Click to expand...

Hi,
I've tried that already but made no difference.

The other thing I have noticed is that on the occasions this happens, there is a progress bar on the white bootup screen along with the Apple logo and usual spinning circle.
This progress bar doesn't appear when I reboot or the occasions that I don't see the issue.

Try repairing the hard drive (not permissions). Use one of these three methods:
Resolve startup issues and perform disk maintenance with Disk Utility and fsck (it's an older guide)

or, with Lion, use command-r immediately after startup gong sound to boot the recovery partition, then use Disk Utility to repair the normal startup drive.

Having done a bit more research on the issue it appears to be a fairly common issue and a bug within Lion which occurs if wireless keyboard and mouse are turned on prior to switching iMac on !!

See link to Apple support
https://discussions.apple.com/thread/3216818?start=15&tstart=0