I've tried several solutions I found on the web, but didn't manage to solve a problem.

Since today my laptop won't find my WiFi network, but neighbours' networks are suggested. Another laptop with U12.04 does find one.

What do I do?

I've Dell Latitude-E4310,

02:00.0 Network controller: Broadcom Corporation BCM4313 802.11bgn Wireless Network Adapter (rev 01)
    Subsystem: Dell Inspiron M5010 / XPS 8300
    Flags: bus master, fast devsel, latency 0, IRQ 17
    Memory at f2c00000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: brcmsmac
    Kernel modules: bcma, brcmsmac

also

NetworkManager Tool
State: connected (global)
- Device: eth1 -----------------------------------------------------------------
  Type:              802.11 WiFi
  Driver:            wl
  State:             disconnected
  Default:           no
  HW Address:        1C:65:9D:7A:45:5C
  Capabilities:

  Wireless Properties
    WEP Encryption:  yes
    WPA Encryption:  yes
    WPA2 Encryption: yes

Should I provide anything else? Many thanks in advance.