Windows7 64bit many prints

On my old pc (WinXP SP3) i use PDFCreator as the default printer for my ERP software with autosave on a specific folder. It works fine.

Now i have a new pc with Windows7 64bit. If i lauch 1 file it works fine but if i launch many spool simultaneously some files  "are lost" in a random way (es. i launch 20 files and in pdfcretor i see 19 files) .. i don't see errors, the erp "think" it's all ok but i don't see files in the list of waiting files

Any ideas?