This is the Nokia 5730 xpressmusic QWERTY keypads malfunction hardware repair manual.
Each individual keys line paths is being highlighted for quick troubleshooting and check up procedures.
Click here to enlarge

There are two EMI-ESD Filters being used also known as the keypads interface IC, which is located just below the flex cable connector. These two Filter IC's also connected to the NUMERIC keys on flex cable assemblies, including all the switches and button keys.

Here's the connection of each particular keys combined in one particular rows and lines.
Each particular key paths is were connected from the keypad interface IC to each groups of particular ROWs and Column of key buttons connections.

EMI FILTER IC on the right
EMI IC lines / ROW-Columns / Button Keys

A2-A5 - KBR_0 = BACKSPACE , W, E, R , T , Y ,U, I , O

D2-D5 - KBR_1 = A , L , D , F , G, "APOSTROPHE" , "PERIOD" , C , S

B2-B5 - KBR_2 = Z , X ,K ,V , B , N , M , / , CTRL

B1-B4 - KBR_3 = Fn , LShift , "COMMA" , J ,SPACE, RShift, Chr , [ ( FLEX ) 4 , 7 ]

C2-C5 - KBR_4 = Q , ENTER [FLEX- SELECT, VOL UP , VOL DOWN , GAME_KEY1 ,
GAME_KEY2 ] ,

C1-C4 - KBR_5 = @ , [FLEX -1 , 2, 3 , SOFT LEFT, CANCEL , MENU , 8 , 9 ,]

D1-D4 - KBR_6 = H , [FLEX - 0 , 5 , 6 , Soft right , Select , Send , * , #

A1-A4 - KBR_7 = [FLEX- MUSIC_KEY1 , MUSIC_KEY2 , LEFT , RIGHT , UP ,
DOWN , MUSIC_KEY3

E1-E4- KBC_0 = [FLEX- 0 , 1, SELECT ] , FN, Z , A , BCKSP

E2-E5 -KBC_1 = [FLEX- MUSIC_KEY1 , 5 , 2 ], Q , LShift , X , L , W

END/power key = POWERKEYX
EMI Filter IC on the left
EMI IC lines / ROW-Columns / Button Keys

A2-A5 =KBC_2 = [FLEX- MUSIC_KEY2 , 6 , 3], ENTER , 'COMMA' , K , D , E

A1-A5 =KBC_3 = [FLEX- LEFT , VOL UP], H , @ , J ,V , F , R

B2-B5 =KBC_4 = [FLEX -RIGHT , SOFT RIGHT , SOFT , LEFT, VOL DOWN], SPACE , B , G , T

B1-B4 =KBC_5 = [FLEX -UP , SELECT , CANCEL , SHIFT , N , APOSTROPHE , Y

C2-C5 =KBC_6= [FLEX- DOWN, SEND , MENU], CHR, M , PERIOD , U

C1-C4 =KBC_7= [FLEX -MUSIC_KEY3 , * ASTERISK , 8 , GAME_KEY1, 4 ], /, C , I

D2-D5= KBC_8= [FLEX- # , 9 , GAME_KEY2 , 7 ], CTRL , S , O
This IC also shares 3 lines for LCD display data signals which is the following:
DISPLAY SIGNALS
D1 - D4 = TE
E1 - E4 = D/CX
E2 - E5 = RESX

GROUNDS = A3,C3, D3, E3
Just analyze on a particular keys which is not working and trace the line across the PCB layouts. Replace the EMI Filter or the keypads interface IC, this chips are most commonly get damaged due to Electrostatic Discharge and Electromagnetic Interference.
If the numeric, navigation or the key buttons which are connected on the flex cable are not working, might check or then replace the flex cable as necessarily.