Dear Jan,
WILCO, checked. Exceptions in Defender (temporarily disabled anyhow) and Kaspersky for the whole X-Plane directory are effective. Just deleted and re-installed IXEG 737; no change in behaviour. Just tried to programme a flight LOWG (Graz) to EDDT (Berlin-Tegel; Air Berlin does this one in real life, though with a Dash 8...). While programming the route, next airway (e.g. UZ33 from LNZ) is accepted quickly when pressing the appropriate LSK (left-hand column), while next waypoint (e.g. ADLET) takes several seconds to appear when pressing the appropriate LSK (right-hand column). The closer to EDDT, the longer the delay. Once the tanks are full and the PERF page is open, things get real bad: ZFW takes 10 seconds to appear in the appropriate box, so does CI and so on. I enclose the FMC debug file which was created when I quit at that point.
Edit: And just to clarify, the system configuration concerning defender and Kaspersky is the same as it was before. IXEG 737 was working fine up to and including versions 1.0.7. (737) and 10.50 (XPlane). Problems appeared only after update to 10.51 (XPlane).
Best
Sigmar
IXEG_FMS_debug.txt