if your print filename is 'something.pdf' and you you make
report form somereport to file (something)
you with realize that acrobat5 prints to a file somthing.pdf.pdf !!!

until acrobat 4 you made something like

myfile='something.pdf'
finalfile='finalname.pdf'
report form somereport to file (myfile)
rename (myfile) to (finalfile)

if you do the same under acrobat 5 you will find following files:
somthing.pdf (=empty)
finalfile.pdf (=empty)
something.pdf.pdf (with the expected report)

you can try following workaround:

myfile='something.'
finalfile='finalname.pdf'
report form somereport to file (myfile)
rename (myfile+'PDF') to (finalfile)

now finalfile shows the expected report.

I do not know if there is a way how acrobat does not add .pdf to your filename.
If you find somthing let me know.