Corel files takes much longer time to open some files

My problem is that when i open some of the files in corel it takes a very long time to open i.e approx 7 to 10 mints even for file size of around 500 kb.

 When we open any of the cdr files given by outsiders it opens up within 3 mints for a file size of around 60-70 Mb. Is their any setting in corel to reduce this time? or is their any other solution to this?

 This is not the case for all the files, if we check some of our older files from backup it works fine. I have set the memory as 50% of RAM. I am working in Corel 11.0. (on PC platform) Also tried to format the harddisk & re installing the corel, still same problem is observed

Request all to give the solution