This issue looks to be a known bug to be patched in next release.

Here are the details from HP Knowledge Base:

Title:
Test description changes lost when moving from details tab to steps tab in test plan
Document ID:
KM1409699
Product:
Quality Center
Version:
11.00
OS:
Windows
Updated:
2012-Aug-01
Classification:
Known Problem
Status:
Action
In plan:
Yes
Submitted:
2012-Jun-19

Change request lifecycle:'

Submitted => Investigation => Action (current state) => Completed (next state)

Customer symptom
Defect ID: QCCR1J24516

Problem:

This is a regression - started from SP3, didn't happen in patch 7 and below.

The scenario is:
- copy a test
- modify description on copied test or any other field in the Details tab of the test.
- move from details tab to steps tab
- modify a step
- go back to details tab of the test, all modifications there are lost.

Solution:

Limitation: None
Customer resolution
The patch is the final fix for this issue.
Fix Version
Release Status
11.00 Action
In the queue for consideration in a future release, patch or hotfix