Certain magnet links are stuck on 'Downloading metadata'.
Restarting the torrent do not work. Pause and Start.
Restarting qbittorrent do not work.

It shows many seeds and peers but it is not fetching the torrent file.

Both uTorrent and Tixati is able to download the torrent file.

Which qbt version and OS are you using?

qbt v3.1.10
Windows 7 64-bit

What does the peers button show? Does it try to connect to any peers?
Does the log say anything relevant? (view->execution log)
I don't suppose you hit your queue limits?

Peers button:
Many peers, none with 100% A quite a few with 0%
Flags:
H P
X P
X H P
X

Using both BT and uTP connection.

execution log - General:
Do not say anything.

execution log - Blocked IPs
Do show something interesting.
The same IPs are getting blocked over and over again.
Is that normal behavior?

I do not know what 'queue limit' is. I have not enabled any such settings. Is that on by default?
Other torrents download just fine.

Try pausing everything except the magnet. Does it download?
Have you set an ipfilter? If yes, it probably blocks those ips.

'Try pausing everything except the magnet. Does it download?'
I've tried that. Doesn't work.

I do not use ipfilter.

Can you update to v3.1.11 and try again?

Updated and tested. Still the same behavior.
The ips are getting blocked several times in a row.
eg:
ip1 blocked
ip1 blocked
ip1 blocked
ip1 blocked
ip2 blocked
ip2 blocked
ip3 blocked
ip1 blocked

How are you connected to the internet? ethernet or wifi?

If you want/can, send me 2-3 of those magnets links via email to sledgehammer999 (at) qbittorrent (dot) org.

I am directly connected to internet using ethernet.
No, sorry, I am not allowed to share those magnet links.

I might be able to provide you a build with libtorrent 1.0.x which exposes the reason a peer has been blocked. However only v3.2.0alpha is compatible with libtorrent 1.0.x. Are you using a private proxy? Are you allowed to use v3.2.0alpha or do they do version whitelisting?

'Are you using a private proxy?'
Sometimes. Why do you ask? Do not the alpha support it?

'Are you allowed to use v3.2.0alpha or do they do version whitelisting?'
That will not be an issue.

I am willing to try it.

The longer you wait, the less likely I can reproduce the bug.

Can you try my latest alpha build? -> http://builds.shiki.hu/qbittorrent_3.2.0alpha_20141207_78d4258_setup.exe
Now the log shows the reason why an ip/peer was blocked.

Can I install it along side the stable version without corrupting my transfer/torrent/download list and settings?

Only one version is possible. It shouldn't corrupt anything.
You can backup the 2 qBittorrent folders found in(Windows XP):

1. C:Documents and SettingsApplication DataqBittorrent
2. C:Documents and SettingsLocal SettingsApplication DataqBittorrent

and then restore them.

I have installed the alpha version but it do not work. It will hang and use 100% of one cpu core.
I have a quad core cpu. That means that 12% stable cpu usage is one core.

Here are the stack dump of the two active threads:

10% of cpu

2% of core

I made a new build. Can you test it and tell if you have the same issues?
Link: http://builds.shiki.hu/qbittorrent_3.2.0alpha_20141229_ca2dc325_setup.exe

There is high probability that you don't get any ip blocked messages now. libtorrent had an option where it blocked by default peers using a low port. I have disabled that. More discussion here: http://qbforums.shiki.hu/index.php/topic,2951.0.html

Now it gets as far as showing the UI then it hangs and use 100% of one core.

How did you get that stacktrace?

Via Process Explorer. I always have it running.

Link: https://technet.microsoft.com/sv-se/sysinternals/bb896653

Remind me in the weekend to prepare for you a new msvc build.
Then I want you to create a mini dump from process explorer.
The build you're using is build with gcc and it has different symbols(and I am not sure I'll be able to get the minidump to work with gdb)

Reminder it's the weekend.

Here is an alpha build with latest code and libtorrent version: http://qbforums.shiki.hu/index.php/topic,2344.msg15066.html#msg15066
If you still experience problems, please make a minidump with processexplorer and post the file somewhere. (or email it to sledgehammer999 at qbittorrent dot org)

I have the same problem with version 4.04 on Mac OS. qBittorrent has become essentially unusable, at least on my system. On three popular torrents with over 100 reported seeds, I was stuck at 'downloading metadata' for an hour with no peers or seeds found. I downloaded Deluge onto the same system and set up my proxy info exactly as I have it in qBittorrent, and it started downloading all torrents immediately.

The log doesn't reveal anything interesting as far as I can see; just routine actions such as 'torrent added.'

I'm on 4.1.5 and I have this same problem. I suddenly can't seem to get any to start downloading.

Yea no I will just close this, it was a 2014-2015 issue. Please, if you encounter this, ALWAYS do the network troubleshoot, check wiki, etc. It's 99% that YOUR setup has some kind of issue and it is NOT a bug.