Your antivirus is throwing off a false positive. You don't have a trojan in that file. Nothing attached itself to it. No matter what A-Squared is telling you about that file, it's wrong. Nothing corrupted your copy of the program.
Does A-Squared have anything within the application for uploading "infected" files to them to be checked and verified? If it does, please submit the file to them so they can fix the problem in their software.
I just uploaded my copy to Virus Total and let them scan it. It is throwing off some false positives in 3 different products: a-squared, eSafe, and Prevx.
My guess was because I had packed the file with UPX to make it smaller, but after unpacking it and uploading it again, there are still 2 different products (out of 43 different antivirus applications) that are still calling it malware, one of them being A-Squared and the other Ikarus. (weird)
If you would like to take a look at the report, you can view it here:
original packed file: http://www.virustota...48df84402-1243743604
unpacked file: http://www.virustota...9e6040246-1251740543
You can also upload the copy you have here and check it with all 43 different antivirus applications, yourself: http://www.virustotal.com