Hello,
Since the user is experiencing this on only one system, it is an error local to that system (you have proven this through your recreation of the user's account and through the user being able to issues the same commands on another system without issue)> Since the client has already been uninstalled and reinstalled and registered, we should start to suspect the system settings. This type of error can be seen when the regional settings vary from the regional settings on the server. As documented in HP KM document, try the following:

Possible Cause
Decimal symbols for numbers, currency, time or date Formats on the affected client machine are changed to ' , ' instead of the default value ' . '

Recommended Fix
Change affected machine's Regional and Language settings according to the below steps:
A) For Windows XP based machines:
1. From Control Panel open Regional and Language Options
2. From Regional Options tab select Customize
3. Within Customize Regional Options window change successively Decimal symbol for Numbers, Currency, Time, Date.
4. Confirm all made changed by pressing OK.
B) For Windows 7 / Vista based machines:
1. From Control Panel open Region and Language
2. From Formats tab select Additional settings
3. Within Customize Format window change successively Decimal symbol to '. ' for Numbers,

Error message is thrown when navigating to History tab in QC Requirement Module.
3. Within Customize Format window change successively Decimal symbol to '. ' for Numbers, Currency, Time, Date.
?4. Confirm all made changed by pressing OK.
In case that the above steps does not eliminate the shown error message please consider changing client machine's default format settings to English (United States).

Try the above and see if that fixes the issue.

Thanks,
Dan