IP Routing LAN-WAN backroute missing

[hals]

Can't get this route managed to work, is anybody out there who could share some knowledge?

LAN PC 192.168.10.99
Cisco1003 192.168.10.3
Ascend Max1800 192.168.1.28
Firewall 192.168.1.1

Cisco logs in flawlessly into Max1800.
The Cisco has no problem in pinging and tracing WAN addresses.
The Cisco starts to dial, when PC tries to connect addresses outside the LAN.
The PC sents out the data successfully (checked DNS-Servers logfile).

But no route is built back to the PC.
Pings and traces are running empty behind the Cisco.
Anybody knows what my config is missing? As the Cisco ping/traces nice, I think the error is in the cisco config, not in the ascends.

Thanks in advance for a hint (getting headaches after hours of tries)
hals

The config:

version 11.3
service timestamps debug uptime
service timestamps log uptime

hostname cisco1003
enable password <snip>

username <snip> password <snip>
ip name-server 192.168.1.11
isdn switch-type basic-net3

interface Ethernet0
ip address 192.168.10.3 255.255.255.0

interface BRI0
ip unnumbered Ethernet0
encapsulation ppp
dialer idle-timeout 45
dialer wait-for-carrier-time 10
dialer map ip 192.168.1.28 name <snip> <callno>
dialer load-threshold 200 either
dialer-group 1
ppp authentication pap callin
ppp chap refuse
ppp pap sent-username <snip> password <snip>
ppp multilink

ip classless
ip route 0.0.0.0 0.0.0.0 192.168.1.28
ip route 192.168.1.0 255.255.255.0 192.168.1.28
ip route 192.168.1.28 255.255.255.255 BRI0

access-list 100 deny ip any host 255.255.255.255
access-list 100 permit ip any any
dialer-list 1 protocol ip list 100


line con 0
line vty 0 4
login
end