Periferiche USB non riconosciute

Le periferiche USB collegate al mio portatile non vengono più riconosciute ma sono alimentate. Utilizzo Ubuntu 15.04, come faccio a ricaricare i driver o a forzare il riconoscimento delle periferiche? Grazie, a presto.

Ecco l'output di "lsusb":

Bus 004 Device 003: ID 05c8:0223 Cheng Uei Precision Industry Co., Ltd (Foxlink)
Bus 004 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Con una sola penna USB collegata ho "dmesg |tail":

[   41.615971] radeon 0000:01:00.0: fence driver on ring 0 use gpu addr 0x0000000080000c00 and cpu addr 0xffff88024f5d1c00
[   41.615972] radeon 0000:01:00.0: fence driver on ring 3 use gpu addr 0x0000000080000c0c and cpu addr 0xffff88024f5d1c0c
[   41.617507] radeon 0000:01:00.0: fence driver on ring 5 use gpu addr 0x0000000000072118 and cpu addr 0xffffc900222b2118
[   41.633648] [drm] ring test on 0 succeeded in 1 usecs
[   41.633657] [drm] ring test on 3 succeeded in 4 usecs
[   41.809561] [drm] ring test on 5 succeeded in 2 usecs
[   41.809569] [drm] UVD initialized successfully.
[   41.809638] [drm] ib test on ring 0 succeeded in 0 usecs
[   41.809702] [drm] ib test on ring 3 succeeded in 0 usecs
[   42.480017] [drm] ib test on ring 5 succeeded