Cant Varify/Decrypt files

Ive generated key at 1st machine (WinXP sp3 Gpg4win 2.0.2), signed txt file and exported key.
On the other mashine (Win7 Gpg4win 2.0.2) i have imported key (there was 1 new public key) and when i want to verify file it gives me status: Key NOT valid.
Theres also problem with decrypting files.
When im trying to verify on the mashine where file was signed I get status Valid.