You may be seeing it for the first time and yes something has probably changed to cause that but the problem has always existed. I should know considering how bad my connection is (see attachment

).
You may be able to download these "large" attachments elsewhere even if they are serving the file with a script. However their server configurations are probably allowing scripts to run longer...or allowing connections to stay active longer. Or you could have a faster connection to that server...who knows.
Try this; go to a high traffic site (say dl.qj.net) and download a large file (in the 20mb+ range). Witness your connection time out before your very eyes!
Like I said the solution for lowband users at this site and elsewhere is to use a browser that supports resume. Just this morning I managed to pull down vBdurpal5.3.0.zip in just 7 attempts.
Yes I know it sucks having to babysit downloads...the internet is no longer designed with us in mind.