Error using load: Cannot read file: inconsistent error message

I have saved mat files using the '-v7.3' like

save('my_big_fat_file, 'TT_abc', '-v7.3');

my_big_fat_file has has about 3 GBytes size.

Never had problems opening this files using the command load('my_big_fat_file') until yesterday I ger the message:

Error using load

Cannot read file I:\folder_a\folder_b\folder_c\my_big_fat_file

But if I try a few minutes later it will work perfectly and the file is loaded.

Tried other files of the same batch and size, and sometimes it loads well, others will diplay the mentioned error.

Any help?

Many Thanks in advance

Para