http://publib.boulder.ibm.com/infocenter/clmhelp/v3r0m1/index.jsp?topic=%2Fcom.ibm.rational.rrm.help.doc%2Ftopics%2Ft_calm_assoc_jazz.html

So for Choose Existing you do not see the below fields?

1. Project Area pull down
2. Search by Keyword or Work Item Number or Search by Query radio buttons
3. Type
4. Work Item Number or Words Contained in the Text. Use quotes for a phrase search:
5. Recently Viewed Work Items

Do you have a project selected in the Artifact Container field?

Nope - nothing. Plain white nothing screen.
Sometimes the user can see the Create New screen, but only sometimes and it seems to go away after time. They then have to log out and log back in. Even then there is nothing on the existing screen. No way to search - nothing.
The project was selected - then they Choose Existing - then nothing. None of the things you listed.

Which browser are they using? Officially in RRC V3.0.1 we provide support for IE 7 and 8, as well as Firefox 3.6

The only thing I can suggest is

1. To clear the active logins, cache, and cookies in the browser. Maybe there is some data hanging around that prevents the displaying of the information

2. Check the RRC Licensing - do they have an Analyst license? A contributor should be fine but it is worth testing if not.

This URL includes a table overview of each license

http://publib.boulder.ibm.com/infocenter/clmhelp/v3r0m1/index.jsp?topic=%2Fcom.ibm.jazz.repository.web.admin.doc%2Ftopics%2Fc_license_mgmt_over.html

3. Is the person creating the work item a member of the RTC project area?

4. Failing this, I suggest contact Tech Support, as RRC is providing the dialogue window for RTC to write the information, but RTC is not presenting the information correctly - or does not have the correct authentication. If you contact tech support you might need to provide them the jts and rm log files from the server.