Heres what i did when the ps store could not be accessed from the PS network section off the xmb.
Got to the ps store from the game section off the xmb. Its under 'trophy collection' on my ps3. Selecting it there will load 6 large thumb nails, select one off the these.. I.e oddworld strangers wrath hd..
You will be taken to the purchase page off the store, from here you can select 'view downloads' In the top right had corner.
Take your mw3 disc and written on the right had side under the age rating is a BLES- number, select all off the content including the spec opps missions that has the same number as your disc.
I only downloaded the maps, which didnt work the first time... So had to redownload it all again.
This worked for me..
