Pendrive problem

Hello,

i hv 16 Gb pendrive, when i copy my data on to the pendrive, it copies correctly but after safely removing the pendrive from the system, if i again browse my data on the pendrive, the data is not found there.
Folder remain there with their original names while the files are replaced by names: "±±±±±±±±±±±±" and show 0 bytes.

pls help