podcasts downloaded outside of iTunes + downloading problem in general

[Nameless4ever]

for some reason I'm having trouble with downloads in general in my mac (yep, 1-month-old switcher right here). It's everywhere from itunes to safari's download manager and even software update. what happens is that the download appears to be completed but the files really aren't e.g. when I try to listen to the podcast the 1st few minutes are okay but if I fast forward there's only silence and the progress bar and time left are stuck/stopped.

I've been using Speed Download as alternative ever since.

 

Now, does someone know how to fix this? and is there a way for me to import the podcasts downloaded via Speed Download into the podcast section of iTunes so that it doesn't come up when I'm shuffling music?

 

Thanks in advance!!

 

Update: I just noticed that I can exclude songs in the music tab from shuffling. a valid workaround but still doesn't fix the main problem.