Strange Problem with 4108gl switch and J4908a module

[Udo123]

Hi group,

currently I trying to solve a problem by a customer.
There is one 4108gl switch with two modules (J4908A) on A and C.
The Uplink is on port C21 to the core switch.
So if I plug a client in port C1 and ping a server which is located on the core switch all works fine.
Also I got an IP adresse and can access the internet through a proxy server.
If I plug my notebook in Port A1 which have no uplink I can ping but I can't access the internet. Also it seems to be there is no TCP (telnet..)working..

The client IP range is defined on VLAN 1 and also there is a mangement VLAN xx on both switches defined.
The uplink is for VLAN 1 untagged and for VLAN xx tagged.
I the case of a single forwarding base for the switch 4108gl the problems seems to be here ?!?!

Any help for me ?

Regards
Udo