TreeView is extremely slow on remove/clear operations

[GoogleCodeExporter]

What steps will reproduce the problem?
Search for sessions in a large session list (1000s) or reload sessions.

What is the expected output? What do you see instead?
Reload should be much faster.

What version of the product are you using? On what operating system?
Win7 64, superputty 1.4.0.5

Please provide any additional information below.
The winform treeview is very slow in profiling on remove and clear operations. 
I have attempted to wrap clear in beginupdate endupdate to no avail.

Original issue reported on code.google.com by j...@gimo.co.uk on 29 Apr 2015 at 3:40