Account module: Blank popup when attempting to Select Leads/Contacts

[jniplig]

Environment

Sugar Version: 4.5.1e (Build 1049)
Sugar Edition: SugarOpenSource
Category: Accounts, Leads, Contacts, Import
Operating System: Windows XP Pro
PHP Version: 4.4.4
Database: MySQL 5.0.24a
Web Server: Apache 1.3.37(UNIX)
Browsers: Firefox 2.0.0.6, Safari (for Windows) 3.0.2, IE 6.0.2900

Issue

When attempting to Select a Lead or Contact from the Account detail view the popup window displays no information. When attempting to Select an Opportunity the popup window displays the list of Opportunities to select from as expected.

Potential Cause

First experienced this after performing the following:

1. Exported Contacts list.
2. Imported contacts.csv file into Leads.

All of the imported Contacts appear in the Leads module, however, they are not associated with the Account that the Contact was associated with. During the import process the Account Name field was mapped properly, as the Account Name appears in the new Lead record, but the relationship is not reflected in the Account record.

Side Note

All of the Contact/Account/Lead information is being imported from various Excel spreadsheets that my colleagues have been using for the past couple of years. This shouldn't really be an issue since I have been importing and exporting directly from the Client module...

Any thoughts??

Thank you in advance!!

Jeremy