Download behaviour problem (updated)

Hi! Thank you for the great plugin. However, I’ve been having trouble with the download feature.
When I try to download from the download page, such as this one:

The browser attempts to open the file as a text file instead, so it shows up as a super long page of meaningless text until it crashes the browser sometimes. And this is not just happening to the Chrome browser in my computer. But also any other browser used in any other computer.

EDIT: I also tried disabling all the other plugins in my site, but its still the same. However, the file downloads properly in IE, when I check the encoding of the download link, it says its a text/html content type.

Everything else is working perfectly.

Would you please help me with this?

Also, I tried purchasing the Pro version, but somehow paypal rejected the transaction. Do you have any other payment methods available?

Hi, the 2co link doesnt work and you didnt answer my first question though. Could you please help me with the first problem? I also found this in the debugging console:

[Wed Jul 02 19:25:34 2014] [error] [client 180.178.96.114] PHP Warning: Cannot modify header information – headers already sent in /var/www/wp-content/plugins/download-manager/functions.php on line 153, referer: http://balitbanghub.dephub.go.id/download/strategi-nasional-transportasi-perkotaan-menuju-indonesia-est/
[Wed Jul 02 19:25:34 2014] [error] [client 180.178.96.114] PHP Warning: Cannot modify header information – headers already sent in /var/www/wp-content/plugins/download-manager/functions.php on line 154, referer: http://balitbanghub.dephub.go.id/download/strategi-nasional-transportasi-perkotaan-menuju-indonesia-est/
[Wed Jul 02 19:25:34 2014] [error] [client 180.178.96.114] PHP Warning: Cannot modify header information – headers already sent in /var/www/wp-content/plugins/download-manager/functions.php on line 155, referer: http://balitbanghub.dephub.go.id/download/strategi-nasional-transportasi-perkotaan-menuju-indonesia-est/
[Wed Jul 02 19:25:34 2014] [error] [client 180.178.96.114] PHP Warning: Cannot modify header information – headers already sent in /var/www/wp-content/plugins/download-manager/functions.php on line 156, referer: http://balitbanghub.dephub.go.id/download/strategi-nasional-transportasi-perkotaan-menuju-indonesia-est/
[Wed Jul 02 19:25:34 2014] [error] [client 180.178.96.114] PHP Warning: Cannot modify header information – headers already sent in /var/www/wp-content/plugins/download-manager/functions.php on line 157, referer: http://balitbanghub.dephub.go.id/download/strategi-nasional-transportasi-perkotaan-menuju-indonesia-est/
[Wed Jul 02 19:25:34 2014] [error] [client 180.178.96.114] PHP Warning: Cannot modify header information – headers already sent in /var/www/wp-content/plugins/download-manager/functions.php on line 158, referer: http://balitbanghub.dephub.go.id/download/strategi-nasional-transportasi-perkotaan-menuju-indonesia-est/
[Wed Jul 02 19:25:34 2014] [error] [client 180.178.96.114] PHP Warning: Cannot modify header information – headers already sent in /var/www/wp-content/plugins/download-manager/functions.php on line 159, referer: http://balitbanghub.dephub.go.id/download/strategi-nasional-transportasi-perkotaan-menuju-indonesia-est/
[Wed Jul 02 19:25:34 2014] [error] [client 180.178.96.114] PHP Warning: Cannot modify header information – headers already sent in /var/www/wp-content/plugins/download-manager/functions.php on line 160, referer: http://balitbanghub.dephub.go.id/download/strategi-nasional-transportasi-perkotaan-menuju-indonesia-est/
[Wed Jul 02 19:25:34 2014] [error] [client 180.178.96.114] PHP Warning: Cannot modify header information – headers already sent in /var/www/wp-content/plugins/download-manager/functions.php on line 180, referer: http://balitbanghub.dephub.go.id/download/strategi-nasional-transportasi-perkotaan-menuju-indonesia-est/