Un-Logic negative total float

Dear Engineers ,

I am working on a recovery plan , so I finished my portion of yesterday(made relations, activities,durations.....) with zero total float , the point is here when I opened the schedule today , a huge -ve total float was appeared...

part 2 of my problem i faced an error message contains :

Date: 04-Mar-15

Executable: PM.exe
Application: Primavera P6 Professional R8.2
Event Code: PRMDB-3310-B
Message:
PRM DBAccess Error: ORA-30036: unable to extend
segment by 8 in undo tablespace 'UNDO'


Context:
1: TDevxMainForm.BeforeFormShow
2: TDevxMainForm.BeforeFormShow
3: TDevxMainForm.BeforeFormShow
4: TDevxMainForm.BeforeFormShow
5: TfrmEPS.mnuOpenProjectClick
6: TCFormManager.SetToolbar
7: TDevxMainForm.BeforeFormShow
8:
9:
10:

Detail:
Type: EprmDBSQLExecutionFailure
Object Type: TCVirtualQueryGrid

Database Error:
Error Code: 0

This appear when using import .

Your efforts is really appreciated .............