NuGet problems with Mono 2.11.2+

#### Show relevant context ####

$ ls
NuGet.exe  packages  packages.config
$ md5sum *
10da026b95c853933c450c5b36024866  NuGet.exe
md5sum: packages: Is a directory
456f53acff20249725f747f7311899fb  packages.config
$ cat packages.config
<?xml version="1.0" encoding="utf-8"?>
<packages>
  <package id="Gate" version="0.3.1" />
  <package id="Gate.Adapters.Nancy" version="0.3.1" />
  <package id="Gate.Builder" version="0.3.1" />
  <package id="Gate.Middleware" version="0.3.1" />
  <package id="Nancy" version="0.9.0" />
  <package id="Owin" version="0.7" />
</packages>$
$
$ mono NuGet.exe help
NuGet Version: 2.1.31002.9028
usage: NuGet <command> [args] [options]
Type 'NuGet help <command>' for help on a specific command.

Available commands:
[snip]
$ mono --version
Mono JIT compiler version 2.11.2 (tarball Wed Jul 25 11:40:11 BST 2012)
Copyright (C) 2002-2012 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
	TLS:           __thread
	SIGSEGV:       altstack
	Notifications: epoll
	Architecture:  x86
	Disabled:      none
	Misc:          softdebug
	LLVM:          supported, not enabled.
	GC:            Included Boehm (with typed GC and Parallel Mark)

#### Test run with Mono 2.11.2 ####

$ time mono NuGet.exe install packages.config -OutputDirectory packages
Successfully installed 'Gate 0.3.1'.
Successfully installed 'Gate.Adapters.Nancy 0.3.1'.
Successfully installed 'Gate.Middleware 0.3.1'.
Successfully installed 'Nancy 0.9.0'.
WARNING: Could not connect to the feed specified at 'https://nuget.org/api/v2/'. Please verify that the package source (located in the Package Manager Settings) is valid and ensure your network connectivity.
The specified archive is invalid.

real	1m50.502s
user	0m1.336s
sys	0m1.528s
$ time mono NuGet.exe install packages.config -OutputDirectory packages
Successfully installed 'Gate.Adapters.Nancy 0.3.1'.
Successfully installed 'Nancy 0.9.0'.
Successfully installed 'Gate 0.3.1'.
Successfully installed 'Gate.Builder 0.3.1'.
WARNING: Could not connect to the feed specified at 'https://nuget.org/api/v2/'. Please verify that the package source (located in the Package Manager Settings) is valid and ensure your network connectivity.
The specified archive is invalid.

real	1m55.538s
user	0m1.276s
sys	0m1.312s

#### Switch to Mono 2.11.1 ####

$ mope global 2.11.1
$ mono --version
Mono JIT compiler version 2.11.1 (tarball Tue Jun 19 11:15:02 BST 2012)
Copyright (C) 2002-2012 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
	TLS:           __thread
	SIGSEGV:       altstack
	Notifications: epoll
	Architecture:  x86
	Disabled:      none
	Misc:          softdebug
	LLVM:          supported, not enabled.
	GC:            Included Boehm (with typed GC and Parallel Mark)

#### Test run with Mono 2.11.1 ####

$ time mono NuGet.exe install packages.config -OutputDirectory packages
Successfully installed 'Gate.Middleware 0.3.1'.
Successfully installed 'Nancy 0.9.0'.
Successfully installed 'Owin 0.7'.
Successfully installed 'Gate 0.3.1'.
Successfully installed 'Gate.Builder 0.3.1'.
Successfully installed 'Gate.Adapters.Nancy 0.3.1'.

real	0m17.546s
user	0m1.640s
sys	0m1.692s
$ time mono NuGet.exe install packages.config -OutputDirectory packages
Successfully installed 'Gate.Adapters.Nancy 0.3.1'.
Successfully installed 'Gate.Middleware 0.3.1'.
Successfully installed 'Gate.Builder 0.3.1'.
Successfully installed 'Nancy 0.9.0'.
Successfully installed 'Owin 0.7'.
Successfully installed 'Gate 0.3.1'.

real	0m15.682s
user	0m1.180s
sys	0m1.268s
$