Several have reported having similar problems, especially when downloading with a slow connection.
A few questions:
Can you download other large files successfully (like progeCAD Professional)? Have you had this problem before with other large downloads?
Where are you located?
What is your download speed?
What kind of connection do you have (ADSL, CABLE, DIALUP, T1/E1 etc)
What time of the day did you try it?
What kind of anti-virus are you running?
What browser are you using? Have you tried downloading the same file with another program like wget?
**Note: In future please post this in the progeCAD Forum