Its a long time since this question has been posed; but I faced the same problem yesterday, and searched for a solution on the net. There are a lot of technical details floating about, and the original poster has referenced the issue on the drupal.org site; though the remedies pertain to Drupal 6.
The solution for Drupal 7 is as follows:
goto administration >> configuration >> content authoring >> text formats
In 'text formats' there are editable options for 'full html', 'plain text', and 'filtered html'. Clicking on each, at the bottom, there's the sub-section 'Filter Settings' and over here you can change the 'Maximum link text length' from its default value of 72 char to anything you fancy 147, 255, 257, etc.
On my site, this resulted in a successful use of the one-time login link which was full and unbroken.